OBJECTIVE To estimate the percent of laboratories with precision performance sufficient to satisfy the operating specifications and guarantee the quality required by the proficiency testing criteria defined by the Clinical Laboratory Improvement Amendments of 1988 (CLIA). METHODS Cumulative distributions that describe state-of-the-art laboratory imprecision were obtained for 1500 laboratories participating in the 1990 College of American Pathologists Quality Assurance Service. Allowable imprecision was estimated from the x-intercepts of charts of operating specifications prepared for commonly used single and multirule quality control procedures having two to four control measurements per run. METHODS The derived values for allowable imprecision were imposed on the cumulative distributions to obtain graphical estimates of the percent of laboratories satisfying the operating specifications. RESULTS Up to 28% of laboratories achieve the imprecision allowable for albumin, up to 64% for total bilirubin, 52% for calcium, 35% for chloride, 48% for cholesterol, 28% for cortisol, 84% for creatinine, 9% for digoxin, 61% for glucose, 64% for high-density lipoprotein cholesterol, 88% for hemoglobin, 95% for potassium, 66% for total protein, 18% for sodium, 29% for thyroxine, 87% for triglycerides, 35% for urea nitrogen, and 81% for uric acid. CONCLUSIONS Improvements in precision are still needed for many laboratory tests to assure the analytical quality required by the CLIA proficiency testing total error criteria.