Fertility of artificial insemination is relatively low when frozen semen is used in sheep (Ozturkler et al., 1999; Sanchez-Partida et al., 1992). Jones and Mann (1977) have suggested a relation between the lipid peroxidation formation in spermatozoa and quick decrease in motility and phospholipid loss in the membranes. Some researches agreed that dialyzed egg yolk, bull seminal plasma, milk and sodium sulphate could prevent spermatozoa from the post-thaw side effects of lipid peroxidation (Salamon and Maxwell, 1995; Aswort et al., 1994; Barrios et al., 2000). Jones and Mann (loc. cit.) claimed that egg yolk could decrease the peroxidation rate of ram spermatozoa when added to extenders but not as much as the bull seminal plasma. Researchers have found that bull spermatozoa can easily peroxidase due to the high level of unsaturated fatty acids bound to the phospholipids in the seminal plasma. The present study is planned to investigate the effects of bull seminal plasma in semen extenders during freezing of ram semen and its post-thaw motility and morphological characteristics.