The objective of this study was to find out the effects of season on semen quality parameters and enzymatic activity of aspartate aminotransferase (AST) in the fertile hybrid AI boars (n=139 ejaculates) in a period of 4 years. Semen volume, sperm motility, sperm concentration, percentage of morphologically abnormal spermatozoa (MAS), total number of spermatozoa per ejaculate and the AST activity in supernatants and in spermatozoa was assessed. Boars were divided into four groups according to season period of the year: winter (1st-3rd month), spring (4th-6th month), summer (7th-9th month) and autumn (10th-12th month). Sperm motility was significantly higher (P