Explicit strategies (protocols) were prepared by the staff of a primary care clinic for use as professional standards by physicians, nurse practitioners and physician's assistants to improve care and facilitate quality assessment in cases of urinary tract infection and upper respiratory illness. Over a 2-year period, audit of 3,442 records for adherence to protocol guidelines revealed a variation with time of 38 to 100 per cent in checklist utilization and 55 to 100 per cent in compliance with specified procedures. Shifting patterns of clinic load and alterations in feedback mechanisms to providers had little relation to guideline adherence. The range in scores was attributed to patient symptom variability with subsequent difficulty applying explicit strategies, and to failure of providers to record details contributing to clinical decisions. With this range of “success” following self-imposed predefined strategies, it is not surprising that retrospective record reviews using short sample periods and criteria established by outside expert panels document wide variation in quality.