Since religious demography has been removed from government censuses as of 1967, reliable statistics on religious affiliation are difficult to obtain. Sociologists and religious leaders estimate that between 30% and 40% of the total population are Christian and that about an equal percentage are Muslim. The Christian churches represented include Roman Catholic; Pentecostal, Protestant, Seventh-Day Adventist, the Church of Jesus Christ of Latter-Day Saints, and Jehovah's Witnesses. A majority of the Muslims are Sunni, while others belong to one of several Shi'a groups. On the island of Zanzibar, about 98% of the inhabitants are Muslim.
Though the constitution forbids religious discrimination, many Muslims believe that they are disadvantaged with less representation in civil service, government, and other public institutions. Some Muslims also believe that Christian students are favored over Muslims in the government-run schools. A number of fundamental Muslims argue that the government is attempting to institute a Christian state. Fundamental Muslim groups on Zanzibar have initiated highly confrontational, anti-Christian proselytizing campaigns, and Christian fundamentalists have responded by calling Muslims "servants of Satan." Tension also exists between fundamental and moderate Muslim groups, as the fundamentalists criticize secular Muslims who drink alcohol and marry Christian women. The growing tensions have not been addressed by the government.