In 1998, treatment completion was low among chlamydia and gonorrhea cases reported to the San Francisco Department of Public Health and assigned for treatment follow-up. To improve treatment completion among growing numbers of chlamydia and gonorrhea cases, the department implemented field-delivered therapy (FDT), a single-dose, directly observed therapy protocol for uncomplicated chlamydial and gonococcal infections. After the protocol was implemented in March 1999, the proportion of cases completing treatment increased significantly, from 61.8% in 1998 to 81.0% in 2000. The greatest increases in treatment completion were observed for females and individuals younger than 20 years old. FDT is an effective, feasible, and convenient way to reach and treat individuals who are unlikely to return for chlamydia and gonorrhea treatment.