Abstract: This study was carried out in national Stud in Tiaret West of Algeria to understand and to evaluate the normal sexual behavior and libido of stallions (Arabian vs. Barb) while mounting a mare in estrus. Eighty-four stallions were divided to two groups from 5-24 years age (n = 47 Arabian; n = 37 Barb). Results revealed significant differences (p<0.05, p<0.01, p<0.001) in sniffing, libido score, flehmen response; time to first mount with erection, number of mounts to ejaculation and mount time for ejaculatory reaching a mean value of (19.15±10.76; 12.23±2.68; p<0.01) second respectively for Arabian an Barb stallion. These stallions were tested in exactly the same place and conditions allows us to discard any side effects due to animal management or any other confounding bias. Our study provided us the knowledge of sexual behavior under Algerian conditions and the distinction between Arabian and Barb stallion.