Nandi greetings involve long, ritualized questions and responses about the health of your children, cattle, farm and home before coming back to a detailed discussion about a major rationale for adult life--children. Lots of them.

The Nandi are not unique in Africa for their love of large families. Most African countries are still plagued by rudimentary health services that cause high rates of infant mortality. So children are precious. In some societies, they are not weaned until they are 4 years old or given a name until they are 5 and felt to be well out of danger. Couples plan on having many children to ensure that some of them live.

However, Kenya has been exceptionally successful in reducing the death rate of children in their first year of life by 25 percent in the past decade, down to 80 deaths per 1,000 infants born, one of the lowest mortality figures in Africa.

But therein lies a potentially explosive problem. The tradition of having large families persists, and -- with more babies surviving -- Kenya's annual 4.1 percent population growth rate is one of the highest in the world. It threatens eventually to outstrip the nation's economic resources.

The short-term ramifications, a doubling of its almost 18 million population by the 1990s, have frightened the Kenyan government. President Daniel arap Moi rarely allows a public speaking opportunity to pass without raising a very unpopular subject -- birth control, or family planning, as it is called euphemistically in conservative Kenya. Officially, the Kenyan population has grown from the 15.3 million counted at the last census in 1979 to 17.2 million, but population experts say the real figure today is approaching 18 million.

While working as a Peace Corps volunteer teacher in Kenya's Nandi district in 1969 and 1970, I was also a local census supervisor for the August 1969 count. It was a sophisticated operation using Nandi teachers and high school students to hike the long distances between homesteads over Nandi district's many verdant hills and valleys.

Each family, as a rule, keeps cattle and plants acres of corn, so people live on their small- and medium-sized farms rather than in villages. Trading centers, like the one here in Kilibwoni, generally consist of shops, restaurants, bars and corn-grinding mills. Their owners leave each evening for their homesteads.

The nation's population back then was 10 million people, with an unalarming 3.3 percent annual population growth rate, closer to Africa's yearly increase of 2.7 percent.

Just what impact Kenya's accelerating population growth has had in the intervening years was vividly obvious when I recently revisited Kilibwoni, 184 miles northwest of the capital, Nairobi. After turning off the Nakuru-to-Eldoret highway onto a new, partially completed tarmac road leading into the Nandi hills, I first was struck by how many new cement-walled and corrugated-metal-roofed houses had sprung up, a sure sign of income growth.

Yet the houses were much closer together, making the homesteads appear as if they were crowding each other. Patches of primordial forest that I had meant someday to explore are now squared acres of corn or cropped-grass cow-grazing land. Several friends' farms have been subdivided into smaller units as fathers died and sons were apportioned their shares. A census taker would not have far to walk from house to house today and could accomplish in hours what took days 13 years ago.

"Land? There is no more land," said Agnes Ronoh, waving an arm toward the crowded, patch-quilt mosaic of small farms at Kibetbetiet. "The land is full," she said sadly. "The future is education."

Agnes and her husband, David, have eight children. The oldest boy, Kipchumba, 16, attends Kaiboi Technical School near their home.

"Land will be too expensive to buy when he is finished with school," Agnes continued. "He is at Kaiboi because we felt it was better that he get a skill rather than have an academic degree and be unemployed."

With some friends you know it is not acceptable to talk about family planning in mixed company, so I gently raised the issue with David when we were alone.

"Nandi customs have nothing to do with this Western business about family planning," David said, eyes angrily flashing. "Family planning medicine is dangerous," he added. David said he personally knew of women who had died or been made seriously ill either by intrauterine devices or oral contraceptives.

David's attitude toward family planning is not uncommon in the Kenyan countryside, where birth control has met the stiffest resistance and where 85 percent of the population lives. Years ago economics forced working- and middle-class urban couples, however, to reduce their families' sizes to two or three children. Nairobi has a low birth-rate growth of 2 percent annually. Still, the economic strictures on large families are beginning to be felt in the countryside, a point indirectly acknowledged by Agnes Ronoh and one that friends in Kilibwoni with rising incomes said was their main reason for beginning family planning.

Only 20 percent of Kenya, the highlands, is fertile, arable soil. Overcrowding already has pushed families onto the fragile, marginal border soils that rapidly deteriorate into wastelands after one or two growing seasons.

With approximately 250,000 youths leaving school each year and a slowdown in the economy, Kenya is facing a growing problem of what to do with idle, unemployed youths. Fifty percent of the population is under the age of 15.

Some leading members of the government have grown vociferous about the rejection of family planning by large numbers of Kenyans. A couple of years ago, the dapper, blunt-spoken Charles Njonjo, minister of constitutional affairs, sparked a heated parliamentary debate by declaring that Kenyans should stop "breeding like rabbits." Last month, Njonjo raised a smaller storm in Parliament by suggesting that Kenyan couples follow his example and limit themselves to three children.

In a nationwide speech late last month, President Moi said that "as long as human numbers here continue to increase at the present alarming rate, growing economic problems with their social consequences are quite inevitable." For the sake of "future generations and the nation in general, we must somehow bring down the rate of increase in our population to a figure which we can support," Moi added.

A National Council on Population and Development, funded with $11.5 million from Kenya, the United States and Britain plus the World Bank and the United Nations, has recently been created under Vice President Mwai Kibaki. The council's first task will be to tackle the widespread misinformation about the side effects of birth control methods.

Ironically, Kenya finds itself in this predicament because its rural health care, maternity clinics, educational programs on nutrition and its healthy, temperate highland climate have all combined to reduce infant mortality dramatically.

"The real reason for Kenya's population spurt is the drop in infant mortality. People are not having that many more children, but more children are surviving," said a Nairobi-based population expert who declined to be identified.

Kilibwoni's health center, with a newly completed maternity wing, two women nurses and a male paramedic, is an example of the type of exceptional health care that is common in rural Kenya but still rare in many parts of Africa.

My friends from Peace Corps days, Richard arap Mwei and Cleophas arap Moro, first surprised me with the size of their families and then by telling me that they have now decided to have no more children. Both men are among the more progressive farmers around Kilibwoni; their incomes, an annual average of $1,400 for Richard and $2,500 for Cleophas, are considerably higher than many of their neighbors'. Yet in each man's case the basis for their decision is economic.

Richard, 36, and his wife, Priscilla, 30, have seven children. The oldest is 14 and the youngest is 4 months old.

"We are agreeing with this family planning because high school fees are $200 to $400 a year," said Richard. "Those fees are only going to go up, not down, and I want to educate each one so each one can look after himself," he continued. "They will have to try and buy their own land or make do with whatever the situation is when they are adults."

What about the Nandi traditions of husbands with several wives and measuring your wealth in cattle and children that he had taught me so much about as part of my folklore lessons? I asked.

"That is history," Richard said, laughing. "Our customs won't feed these children and we'll have troubles if we don't stop," he added soberly. "Priscilla has agreed to take the pill."

Cleophas, 40, and Viola, 35, have six children, their ages stretching from 15 down to 4. I stayed with them, so our late-night conversations were generally more candid.

Each night Cleophas and I would talk as we bent over the Chinese-made kerosene pressure lamp I gave him in 1970. As we struggled to keep the kerosene spray properly adjusted, Cleophas told me the cost of such lamps has risen in the past 12 years from $11 to $29 today.

"You can understand why I'm regretting that I didn't start this family planning earlier," Cleophas said. But they had been slow about it because "we heard this medicine was no good and could hurt Viola," he continued. "We're still not sure about it."

"Around here, a few only have begun," he continued. "Many refuse, but they are usually younger than us. People in their late thirties and early forties have begun family planning, especially when they become aware of the future costs" of living, he said.

Family planning is taking root slowly, "like when [higher yield] hybrid corn first came into this area," Cleophas said. "Many farmers at first refused to plant it, but now everyone plants hybrid corn."