The aim of the study was to analyse the effect of a male mink single-dose hCG stimulation on the libido during the mating season and on blood testosterone levels after the season. The material involved males of American mink. The treatment-group males were administered a dose of 100, 150 or 200 U of hCG. Blood was collected twice, approx. 2 weeks prior to and on the completion of the mating season. The group receiving 100 U hCG had the highest percentage of males effectively copulating with females within the first 24 hours after stimulation, whereas males stimulated with a dose of 200 U hCG showed the lowest libido over the same period. On the other hand, males of the group stimulated with 150 U hCG mated to the highest number of females throughout the mating season. The mean plasma testosterone concentration in all the studied males on 18 February was 12.44 ng/ml. The drop in testosterone concentration at the end of the mating season was significant.