A cross-sectional interview study was made with 290 teachers in 10 high schools in Yazd city, Islamic Republic of Iran. More than 90% of the participants had previously received information about HIV and AIDS. Only 207 (71.4%) correctly answered all questions on methods of transmission of HIV/AIDS. Most knew about sexual contact (93.1%) and infected blood (92.1%) as methods of transmission. Some teachers (20.3%) thought that mosquitoes could transmit HIV/AIDS. Regarding attitudes toward HIV/AIDS, over 55% of the teachers agreed or strongly agreed that infected people should be quarantined, whereas 17% agreed or strongly agreed that AIDS is a specific disease of those with high-risk sexual behaviour. Married teachers held more positive attitudes toward HIV/AIDS than unmarried teachers.