Computer-assisted semen analysis: results vary across technicians who prepare videotapes. 
Automated semen analyses revealed differences of 21% to 30% in concentration-related parameters and 5% to 11% in motion-related parameters between means of groups of replicate specimens.  Disparities among videotapes produced by two laboratory technicians accounted for the divergence in concentration-related parameters.  This resulted partially from differences between the two technicians in propensity to dilute concentrated specimens.  The causes of the greater portion of disparities between videotaping technicians, however, have not been identified.  Differences in motion-related parameters could not be ascribed to technicians, but the basis for these differences is also unknown.  The results suggest that values obtained from the CellSoft image analysis system may not be comparable between technicians or laboratories, despite use of identical computer parameter settings.  Until effective quality control measures have been implemented, such comparisons must be made with caution.