Two groups of women under the age of 26 with chlamydial infection (A-asymptomatic women from a screening program, B-traditional STD clinic patients) and their partners were compared with respect to history of STD, sexual behavior, contraception, and indices for income and social welfare expense. The mean number of partners was 1.3 in group A and 1.8 in group B. Women in group B, in spite of more frequent condom use, demonstrated greater risk behavior both with respect to STD and to unwanted pregnancy and also had higher indices for social welfare expense. More group A partners than group B partners were asymptomatic and chlamydia negative. Group B partners also more often had low income as well as high social welfare expense indices. In both groups, complicated chains of transmission were found, and the need for expert contact tracing in both types of patient groups is stressed.