A standard cost-finding methodology was used to estimate the incremental expenses associated with the provision of screening, diagnostic and treatment services for N. gonorrhoeae and Chlamydia trachomatis in a family planning clinic serving high risk adolescents. The study included both the personnel and nonpersonnel costs accrued in administering screening and diagnostic tests, contacting patients with infection, treating patients with infection, and administering tests of cure. The cost per screening test averaged $9.74 when part of a routine family planning visit. Diagnostic tests provided to drop-ins with symptoms averaged $19.92. Treatment-related costs per visit averaged $24.97. The total incremental cost of providing STD screening, diagnosis, and treatment services in the clinic represented 14% of the clinic's overall budget during the study period.