The aim of this study was to investigate whether the quality of semen has deteriorated during the last decade. Laboratory records containing semen analysis results were reviewed. The records, arranged according to date of birth, are kept in shelves. Every fifth record for analyses performed between 1985 and 1995, and only those of men in infertile relationships, were included. The data were abstracted in a data base, and time-related changes in semen characteristics were studied using linear regression analyses. During the study period, there was a slight, but significant increase in sperm concentration, percentage of motile spermatozoa, percentage of spermatozoa with normal morphology, and the base-value of the penetration test. The seminal volumes decreased slightly, but significantly. Sperm characteristics were not associated with age or date of birth of the men. In conclusion, these data show no evidence of deterioration in sperm quality during the last decade among men in infertile relationships.