Cytogenetic studies were made on 328 spermatozoa from three Individuals using either fresh semen samples capacitated in Biggers, Whitten and Whittlngham (BWW) medium plus human serum albumin (BWW+HSA) or semen samples preserved at 4°C in TEST-Yolk buffer. A total of 261 sperm karyotypes were obtained in a series of experiments in which half of each sample was capacitated in BWW+HSA and the other half in TEST-Yolk buffer at 4°C for 2 days; 123 and 138 sperm karyotypes were obtained from the two capacitation methods respectively. Neither the frequency of sperm chromosoinal abnormalities nor the sex ratio was significantly different after each capacitation method. In one individual, however, the sex ratio (19X:32Y in the fresh sample and 49X:28Y In the preserved sample) did show a significant difference. In three experiments with semen samples from a single individual capacitated at 4°C for 1, 2 or 3 days in TEST-Yolk buffer we obtained 33, 30 and 34 sperm karyotypes respectively. No significant differences in the sex ratio was exhibited between these experiments; the number of chromosome anomalies was too low to allow statistical analysis. Our results suggest that TEST-Yolk capacitation for 1, 2 or 3 days does not induce significant variations in the frequency and type of chromosomal abnormalities in human spermatozoa.