Achieving cancer early-detection goals remains a challenge, especially among low-income and minority populations. A randomized trial based in 62 community health centers for the underserved in New York, New Jersey, and western Connecticut. Family physicians were on staff at most of the centers. Workshops, materials, and ongoing advice for center leaders promoted implementation of a preventive services office system to identify patients in need of services at each visit through use of medical record flow sheets, other tools, and staff involvement. EVALUATION END POINTS: The proportion of randomly selected patients by center who were up to date for indicated services at baseline (n = 2645) and follow-up (n = 2864) record review. Only 1 service (breast self-examination advice) increased more in intervention centers. Seven of 8 target services increased significantly for the 62 centers overall. During the study, the medical director changed in 26 centers (42%). Keeping the same medical director at intervention centers was associated with improvements in services. Cancer early-detection services are improving in community health centers, but the intervention had only a small impact, as determined by record review. To have an impact, the intervention required that there be no change in medical director. The relationship of changes in the practice environment to services delivered is complex and deserves more study.