A re-evaluation of daily sperm output of men.

The daily sperm output (DSO) was reevaluated and urinary loss of sperm was determined. Ejaculates were immediately fixed with glutaraldehyde, stored, and homogenized in a blender to produce a cell suspension. The number of sperm per ejaculate was determined by phase-contrast cytometry. Based on the average number of sperm per ejaculate for the last three of five daily ejaculates, the DSO was 166 +/- 29 X 10(6) sperm for nine men aged 26 to 38 years. Two successive daily ejaculates were sufficient to stabilize extragonadal sperm reserves following accumulation or depletion of epididymal sperm. Sperm were found in urine of three men, and less than 2% of their DSO appeared in the 24-hour urine. Few sperm were voided in the urine of men ejaculating daily; however, the DSO exceeds previous estimates.