The effects of vaccination against gonadotropin releasing factor (GnRF) with Improvac® (Pfizer Animal Health) were compared with surgical castration in fattening pigs.A total of 205 pigs were surgically castrated (group K) and 191 were vaccinated twice (group V) using the boar taint vaccine (Improvac®; 2ml s.c.). The first dose was administered atthe age of 12 weeks when the animals were moved into the fattening unit and the second dose in week 18, 4-6 weeks before the planned slaughter date. Live weights were recorded in weeks 1, 4, 12, 18, and 22. In weeks 18 and 20, length and width of the testicles of 171 animals of group V were measured. After slaughtering cold carcass weight, back fat depth, muscle thickness, percent lean meat, and fat and muscle areas of the carcasses were determined. A piece of the neck muscle from each pig was used to conduct a cooking and melting sensory test.While no significant weight difference was evident in week 22 (K=89.4kg; V=88.6kg), cold carcass weight, and back fat and muscle thickness were lower for vaccinates. Vaccinates had higher average daily weight gains (ADW) after the second injection from week 18 up to the cut-off weighing in week 22 (V=1121g; K=1007g; p<0.001) in contrast to average daily weight gains between weeks 12 and 18 (K=740g; V=668g; p<0.001). After the second injection, testicle size of vaccinated pigs decreased significantly. All animals were negative for boar taint by both cooking and melting tests.Boars vaccinated against boar taint had lower ADW before the second vaccination, but compensated the weight difference after complete vaccination. The significant reduction in the testicle size after the second injection indicates a vaccination success. After vaccination no boar taint was detected in carcasses.Vaccination as well as surgical castration reliably prevents the incidence of boar taint. The late rise in daily gain can be beneficial if management is aligned.