We studied sexual dimorphism in the black forest-steppe viper, Pelias berus nikolskii (Vedmederja, Grubant et Rudaeva, 1986), inhabiting the Voronezh region. From 2008 to 2017, 118 snakes were captured, of which 84 were males and 34 were females. Body length, tail length, and five head measurements were taken from the individuals was calculated. Analysis of Covariance showed that males and females differed in all traits except the greatest width of the head and head length.