The techniques of freezing boar semen in 5 ml straws was evaluated in vitro. Semen was processed and frozen according to the method described by Westendorf et al. (1975). The average post-thaw motility in 72 ejaculates from 3 boars was 21% and the percentage of spermatozoa with normal apical ridges was 54%. A significant decrease in the percentage of spermatozoa with a proper motility and an increase in the percentage of spermatozoa with acrosomal damages were observed during dilution, cooling, freezing and thawing.