An outbreak of 1089 cases of infectious syphilis (primary, secondary and early latent) which occurred in the province of Alberta from 1981 to 1987 was analysed by stage of disease, age, sex, sexual preference and geographic distribution. The majority of cases occurred between 1983 and 1985 inclusive. Men accounted for 75.8% of the study population. The majority of men (71%) and women (98.5%) were heterosexual. Of the infected women, 58.7% were North American Indians and many worked as prostitutes. There was clustering in urban locations with 71.8% and 17.7% of cases reported in Edmonton and Calgary, respectively. Clinical signs of syphilis were more commonly present in men than women. Contact tracing played an important role in controlling the outbreak with 15.9% of men and 44.7% of women being diagnosed and treated as a result of this activity.