To reduce the incidence of gonorrhea in the Colorado Springs, Colo., area, casefinding measures (interviewing of patients and tracing of contacts) were conscientiously applied by the local health department, in cooperation with the U.S. Army, to more than 90 percent of reported cases during a 3-year period. Nearly 4,000 cases of gonorrhea--2,127 civilian and 1,811 military--were interviewed; they named 7,399 contacts. A total of 1,141 cases of gonorrhea were newly identified and patients brought to treatment in Colorado Springs as a result. Implementation of these measures was associated with a 12.9 percent overall decline in gonorrhea incidence. This decline was most pronounced in the civilian population (20 percent), while little change in incidence occurred in the military population. The data presented suggest that the orderly application of casefinding epidemiology, allied with other control program initiatives, can interrupt transmission of, and prevent, disease.