Objective: To determine the level of standardization in performance of the semen analysis among clinical laboratories in the United States. Design: A survey was mailed to laboratories requesting information about the laboratory and performance of the semen analysis. Responses were received from 536 laboratories. Setting: Clinical laboratories enrolled in the American Association of Bioanalysts Andrology Proficiency Testing Program. Patient(s): None. Intervention(s): None. Main Outcome Measure(s): Agreement among laboratories. Result(s): Sixty-one percent of respondent laboratories were part of an assisted reproductive technology program. The laboratories perform less than 50 (53%), less than 10 (25%), or less than 5 (16%) andrology laboratory procedures per month. The laboratories routinely report sperm count (94% of laboratories), motility (95%), morphology (85%) and forward progression (69%), and semen volume (96%) as part of the semen analysis. Only 64% of laboratories routinely report abstinence, and 60% of laboratories indicate the criteria used for sperm morphology on the report form. The most common lower limits of normality for sperm count and motility were >20 X 10(6)/mL (77% of laboratories) and >50% (59% of laboratories), respectively. Few laboratories performed quality control for sperm counts (29%), motility (41 %), and morphology (41 %). Conclusion(s): These data indicate a significant lack of standardization in the performance and reporting of semen analyses among laboratories in the United States. (C) 2002 by American Society for Reproductive Medicine.