The first census ever published by Saudi Arabia reports that the kingdom had a population of 7,012,642 in the summer of 1974.

The Ministry of Finance and National Economy released the results in an official journal last year, but they had limited distribution outside the kingdom and it is widely believed that the government decided to suppress them because the numbers were embarrasingly low.

The Saudis have been sensitive about the subject of a census because they feared just such a result. Experts report that one other census was conducted in 1962 and 1963, but its results were never made public apparently because of the small number of people it showed to be in the country.

The figure of 7 million in the current includes foreigners who live in Saudi Arabia but does not say how many there are. Informed officials estimate that there are well over a million Americans, Yemens, Egyptians, Palestianians, Koreans - a figure that would put the number of Saudi citizens at no miore than 6 million.

Some skeptics beleive even that figure to be too high.

According to the census results, there are 2.7 million residents in the seven cities with populations of 100,000 or more - Riyadh, the royal capital: Jeddah, the diplomatic capital and chief post; Mecca; Tayif; Medina; Dammam and Hoduf. Since much of the rest of this country, which is the size of Western Europe, is uninhabited, these critics find it hard to beleive that there are more than 4 million people outside the cities.

The number of inhabitants in Saudi Arabia and the seize of the work force are among the most sensitive issues here. Lack of manpower is one of the thorniest problems facing, the country as it seeks to leap into the industrial age by implementing a five-year, $142 billion development plan while preserving its conservative, insular traditions.

The country, has been forced to import hundreds of thousands of foreign workers, many of them non-Arab and non-Moslem, and to permit an increasing number of Saudi women to go to work. The five-year plan projects that an additional half-million workers from abroad will be needed to carry it out, workers who will inevitably have an impact on a country where the Koran is the law.

Planning Minister Hisham Nazer acknowledged recently that "we are not doing very well" in training Saudis to taken on the jobs that must be done it the country is to develop.

In many parts of the country, schooling is still rudimentary, except for those who make it to the high-school level. "People prefer formal education to vocational training," he said. "It's free, and it's prestigious. Why be a plumber?"

He called the foreign workers "necessary evil" and put their total number at "not more than 350,000."

Even his Cabinet collegues consider that much too low on estimate. The minister of industry and electricity, Ghazi Quasaibi, says there are about a million "guest workers" and that this number will rise to 1.5 million as new labor comes in to work on the projects of the five-year plan.

He said Saudi Arabia has "no quick answer" to its manpower shortage. "We are counting on guest workers coming from abroad," he said. In granting loans to new industries and issuing factory permits, he said, the government is favoring those will require large amounts of capital or energy, which are plentiful, and discouraging those, such as textile plans, that require great numbers of workers.

Just as sensitive as the issue of foreign labor is the role of Saudi women in the labor force. While most young Saudi girls now go to school, they are still generally not permitted to work alongside men or in places frequented by men. So completely have women been excluded from public life that even the newest government office buildings are constructed without toilet facilities for them because women are not expected to be there.

Whether this tradition of secluding women in the home can outlast the need for Saudi workers is doubtful.

"This issue, is not whether women will work but where," Planning Minister Nazer said. He said there is "no doubt that some professions' are now acceptable" for women, such as teaching or nursing where they come in contact only with other females. But other jobs are still closed to them, he said, and even those who do go to work are under strong social and family pressure to give up their jobs when they marry so they can return to their traditional place in the home.