A survey of 89 random rape cases including 166 semen traces, according to the prostate-specific-antigen test, showed the need for a more efficient method of DNA-profiling. No male autosomal STR-profile could be detected, after differential lysis, in 35% of the 84 samples usually containing high amounts of the victim's cells, i.e. vaginal/anal washings and knickers. A Y-STR-pentaplex was applied to the stored sperm fraction of 50 unsolved semen traces, with success in 48% of them. The chance of success depends of the amount of total DNA available and of the quality of the extracted DNA.