3258 randomly selected household residents of Edmonton, Alberta were interviewed by trained lay interviewers using the Diagnostic Interview Schedule (DIS). The lifetime prevalence of mania was 0.6%, for both sexes combined. Lifetime morbidity risk was 1.4% for men and 0.6% for women. The mean age of onset was 20 years of age for both men and women. Ninety-five percent of bipolar individuals had had their first onset by age 26, and less than 5% had their onset before the age of 10. The mean number of manic episodes was 23. Comorbidity with other disorders occurred in 92% of the manic subjects. Depression (62%), alcohol abuse (45%), substance abuse (35%), and phobias (54%) had an increased lifetime prevalence in individuals with a history of a manic episode(s).