Epidemiological and mouse cytogenetic studies have suggested the existence of a positive relationship between the frequency of chromosomal abnormalities and the duration of male sexual abstinence. A cytogenetic analysis of human spermatozoa was performed with 4 men after periods of sexual abstinence ranging from 2 to 15 days. Using hamster eggs for penetration, 934 sperm chromosome complements were obtained. The overall frequency of sperm chromosomal abnormalities was 9.4%. There was no correlation between the length of sexual abstinence and each type of chromosomal abnormality. Our results do not support the hypothesis of an increased risk of aberration with duration of abstinence.