Article 20 of the 1976 Constitution of Democratic Kampuchea guaranteed religious freedom, but it also declared that "all reactionary religions that are detrimental to Democratic Kampuchea and the Kampuchean People are strictly forbidden." About 85 percent of the population follows the Theravada school of Buddhism (see Buddhism , ch. 2). Before 1975 the Khmer Rouge tolerated the activities of the community of Buddhist monks, or sangha (see Glossary), in the liberated areas in order to win popular support. This changed abruptly after the fall of Phnom Penh. The country's 40,000 to 60,000 Buddhist monks, regarded by the regime as social parasites, were defrocked and forced into labor brigades. Many monks were executed temples and pagodas were destroyed or turned into storehouses or jails. Images of the Buddha were defaced and dumped into rivers and lakes. People who were discovered praying or expressing religious sentiments in other ways were often killed. The Christian and Muslim communities also were persecuted. The Roman Catholic cathedral of Phnom Penh was completely razed. The Khmer Rouge forced Muslims to eat pork, which they regard as an abomination. Many of those who refused were killed. Christian clergy and Muslim leaders were executed.

The Khmer Rouge's treatment of minorities seems to have varied from group to group. The Vietnamese endured the greatest suffering. Tens of thousands were murdered in regime-organized massacres. Most of the survivors fled to Vietnam. The Cham, a Muslim minority who are the descendants of migrants from the old state of Champa, were forced to adopt the Khmer language and customs. Their communities, which traditionally had existed apart from Khmer villages, were broken up. Forty thousand Cham were killed in two districts of Kampong Cham Province alone. Thai minorities living near the Thai border also were persecuted.

Despite the fact that Chinese and Sino-Khmers had dominated the Cambodian economy for centuries and could be considered exploiters of the peasantry, the Khmer Rouge apparently did not single them out for harsh treatment. The war drove most rural Chinese into the cities, and after the forced evacuations they and their urban compatriots were regarded as "new people." They shared the same hardships as Khmers, however. Phnom Penh's close relationship with China was probably a factor in the regime's reluctance to persecute them openly.

In the late 1980s, little was known of Khmer Rouge policies toward the tribal peoples of the northeast, the Khmer Loeu. Pol Pot established an insurgent base in the tribal areas of Rotanokiri Province in the early 1960s, and he may have had a substantial Khmer Loeu following (see The Cambodian Left: The Early Phases , this ch.). Predominately animist peoples with few ties to the Buddhist culture of the lowland Khmers, the Khmer Loeu had resented Sihanouk's attempts to "civilize" them. Cambodia 1e4 a expert Serge Thion notes that marriage to a tribal person was considered "final proof of unconditional loyalty to the party." Khieu Samphan may have been married to a tribal woman.

Data as of December 1987