PIP: Joint meetings between the members of the US Family Planning Services Program and the STD Program of Region X (comprising Alaska, Idaho, Oregon, and Washington) from fall 1986 through spring 1987 led to the screening and treatment of patients with chlamydia. Samples from patients were sent to state health department laboratories in Idaho, Washington, and Oregon. A direct fluorescent antibody (DFA) slide technique was used to process the cervical smears. Clinic visit record (CVR) information and laboratory results were collected by a central data management company, and sent to CDC and Region X researchers. 6 clinics in 3 of the states collected 2 cervical samples from each of 3000 patients, 1 for smear (DFA slide) and 1 for tissue culture over a 4-month period. During the 1988-1990 period, 136 clinics in the region supplied patient information and test results on over 300,000 samples. Overall, positive rates for chlamydia in the region went from a high of 10.9% in the 1st quarter of 1988 to 6.8% in the last quarter of 1990, with an overall declining trend. This amounted to an almost 37% decrease within the region. When analyzed by state, the positivity rates and decreases were relatively similar: Alaska, 12.2% to 10.0% positivity (18% decrease); Idaho, 10.5% to 8.0% (24% decrease); Oregon, 8.9% to 6.9% (22% decrease); and Washington, 9.3% to 6.6% (29% decrease). In patients 17 years of age and younger, positive rates for chlamydia fell 19%, from 12.2% in 1988 to 9.9% in 1990. In women 18-19 years old and women 20-24 years old, the rates fell 24% and 31%, respectively. Larger decreases in chlamydia rates were found among women in the 25-29 year age group (31% reduction) and in those 30 years old and older (44% reduction). Infection rates decreased in all race/ethnic groups, except Asians. Approximately 2/3 of the women with positive chlamydia tests had no apparent symptoms of disease. Conversely, the presence of certain clinical indicators seemed to correlate with the probability of a positive test result.