The authors reviewed all cases of active tuberculosis newly reported to a population-based registry between 1970 and 1985 to compare a large urban area with the mostly rural remainder of the province of British Columbia, Canada. Although incidence rates have declined steadily in the rural area, they have not done so in the urban area. Within the urban area, there was a striking relation between tuberculosis incidence and socioeconomic level. Incidence rates in those born in Canada were observed to be higher for men than for women and higher for men who had never married than for those who had ever married, a difference no longer present within census tract groups. The greatest difference in incidence was between unemployed and employed men. Cases in the poorest census tracts more commonly had advanced, infectious pulmonary disease and were more likely to be alcoholics. The incidence of tuberculosis in the poorest census tracts did not decline as rapidly as in other areas. The characteristics of the disease in the poorest urban census tracts suggest the possibility of selective migration of persons at risk for tuberculosis and of continuing transmission of the disease and call for imaginative case-finding and treatment programs to address this problem.