Emiliano Zapata's revolutionary army rode into this town in 1914 and announced that villagers at last would be given the nearby lands they had been claiming for generations. Seven decades later, the peasants here are still fighting for full possession of those farmlands.

In a bloody clash with Mexico State riot police on April 19, some 300 peasant protesters were forced from a colonial-era estate they had occupied here. Dozens of police and peasants were wounded. A 75-year-old protester, Francisco Garcia Ricano, hospitalized with two broken arms and a broken leg, died from his injuries 10 days later.

The Tequixquiac confrontation was only the most recent violent incident provoked by the problem of an expanding rural population coveting a shrinking arable land supply.

Such conflicts are becoming more frequent, officials and peasant organizations concur, as Mexico winds down what is probably the world's oldest continuing land reform program. These unresolved land disputes are an increasingly acute political and economic problem for a government that has long relied on strong peasant support.

Since the 1910-20 revolution, Agrarian Reform Minister Luis Martinez Villicana informed Congress last year, the Mexican government has distributed 253 million acres to about 2.3 million small farmers. Despite this effort, demographers calculate, there are still about 4 million landless peasants in Mexico -- more than in Zapata's time.

Yet Martinez Villicana reports that with isolated exceptions, the government expects to conclude its distribution program in 1987. "The land is not elastic," he said in an interview. Peasants who fail to get land "will be disappointed, but we are not going to mislead them by pretending that there is enough land for everyone."

Authorities blamed the clash here last month on "extremist agitators" they say blocked the farm's entrance for days and "abducted" overnight two Agrarian Reform Ministry investigators. The peasants, led by organizers affiliated with Marxist opposition groups, claim the police attacked without warning. At least 11 accused protest leaders remain imprisoned and face possible 12-year terms for instigating an invasion of private property.

The 460-acre estate, Tequixquiac residents contend in a case paralleled in scores of similar poor farming communities throughout Mexico, was stolen from villagers by Spanish colonialists. Its sale to private dairy farmers 30 years ago was illegal, they argue.

"We will continue defending the land that our fathers' fathers defended with their blood," declared the crudely printed leaflets distributed during the three-week sit-in at the gates. "They can call us land invaders, but the land is ours. We will not give up."

Embarrassed by the outbreak of violence, Mexican officials promised to reexamine the ancient dispute. But the protesters are unlikely to succeed, the officials acknowledge.

"As government authorities, we can only act in accord with the law," Villicana Martinez said, noting the claim was studied and rejected by government experts as recently as 1972.

Independent experts have long urged a halt to Mexico's land giveaway. "By continuing to hand out poor land to thousands of peasants, they are dooming the agricultural system to failure," said Kenneth Shwedel, chief agricultural economist at the Banco Nacional de Mexico.

More than 90 percent of Mexico's territory is classified as arid or semi-arid, a percentage increased steadily by erosion and encroachment of deserts. The country imports more than 8 millions tons of food annually, including nearly half of its staple grains. Rather than continue to subdivide "a land base that simply cannot support 6 million rural families," the government should aid the development of efficent, modern "production-oriented" farms, Shwedel said.

Although welcomed by many agricultural specialists, the forthright admission that the land distribution program is ending poses a political dilemma. Frustrated land claimants are increasingly willing to throw in their lot with leftist opposition groups, eroding the once monolithic rural base of Mexico's ruling party. Opposition organizers create further difficulties by advocating dramatic protest demonstrations, which can quickly turn violent.

On the day after the clash in Tequixquiac, in cactus-spiked hills 35 miles north of Mexico City, fields were littered with the charred wrecks of bicycles and horse carts that the peasant protesters said had been seized and burned by police. Torn, bloody clothes and scorched protest banners dotted the demonstrators' wrecked campsites.

Estela Zepeda, among those evicted, said her firewood-laden burro had been doused with gasoline by police and burned alive. "They are the ones who attacked us," said Mexico State Police commander Guillermo de la Pena, denying accounts of police abuse. "They sent 13 of us to the hospital."

The government has little incentive to resolve the case in the protesters' favor, political observers note. The chief organizer of the sit-in was the Plan de Ayala National Coordinator, an antigovernment peasant organization linked to Mexico's two biggest leftist opposition parties. The protest "was fundamentally political," a partisan "attempt to provoke a confrontation and win votes" in this year's congressional elections, Martinez Villicana charged.

"This was organized by communists," said Agrarian Reform Ministry spokesman Carlos Martinez. "Everywhere in the world the communists are interested in just one thing -- in taking power. They didn't want to resolve this problem, they wanted to take advantage of it."

The Plan de Ayala group, taking its name from Zapata's revolutionary manifesto demanding "land and liberty" for the peasantry, is "only a small minority, representing perhaps a few thousand people," Martinez Villicana said. But the group has successfully coordinated dozens of peasant protests throughout central and southern Mexico in recent years, often with violent results.

Last year, according to Plan de Ayala and another leftist-led agrarian organization, the Independent Campesino and Workers Confederation, 69 peasants were killed in confrontations with local authorities or with gunmen apparently protected by village political bosses. The appeal of these opposition organizers, some officials acknowledge, stems from mounting peasant bitterness at the unfulfilled promises of government land offices.

"Our parents first presented our case in 1951," said Jose Luis Valencia Rosales of Paracho, Michoacan, pulling a worn set of legal papers from his briefcase. Villagers from Yanaga, Veracruz, announced plans to march to the capital this month to demand lands they first formally claimed in 1935.

A week rarely passes in Mexico City without at least one such demonstration from the provinces. Last month, about 10,000 peasants affiliated with Plan de Ayala chapters converged on the capital to publicize land complaints.

The Agrarian Reform Ministry ruled on about 7,000 land claims in the past year, but more than 6,000 cases remain to be settled, Martinez Villicana said. By one official estimate, more than half of Mexico's settled territory was the subject of claims when the present government took office two years ago.

The Tequixquiac conflict, typical of such disputes, dates nearly to the Conquest. In 1595, villagers say, their community was granted a land title by Mexico's Spanish colonial government, a deed they contend was only partially respected.

"They supposedly have a title from the viceroy, but as far as we know they have never showed it to anybody," said Agrarian Reform spokesman Martinez. "If they could produce the document, then perhaps the case could be resolved in their favor."

The deed is long since lost, villagers say. But in 1914, records show, major general Reyes Castaneda of Zapata's triumphant Army of the South announced that the lands were theirs. Three years later, the revolutionary government reneged, refusing to recognize the general's land award. In 1929, the village was finally deeded more than 8,000 acres, a tract not including the rich stream-irrigated fields of the estate.

The estate was converted in the 1950s into an efficient commercial dairy farm, making Tequixquiac a microcosm of the conflict between Mexico's economic need to modernize agriculture and its social commitment to the peasantry. The dairy produces milk that Mexico would otherwise have to import. Yet it employs fewer than 20 full-time workers, while the lands, if redistributed, could support perhaps 40 farmers growing corn and beans for sustenance.

"They want to take over the estate because it is nice and pretty now," a dairy foreman grumbled. "Before money was spent to make this place productive, nobody cared about it."