Abstract. Leptin gene (LEP), the product of which is an important factor controlling body weight, fat reserve and feed intake, is of great interest for geneticists (XIE et al., 1999; KURYŁ, 2000).

Due to different origin of horse breeds and distinct objectives of their breeding, a question arises whether the polymorphism of leptin is going to be also characteristic for horses depending on their breed and utility type?

In the present research, investigations were undertaken with the aim to detect mutations in leptin gene (LEP) in horses bred in Poland and to determine genetic structure of horses of different breeds and utility types basing on leptin gene (LEP) polymorphism.