To determine sexual dimorphism in spotted gar (Lepisosteus oculatus), variation in standard length, mass, snout length, snout width and body depth was compared between sexes using analysis of covariance. Females were significantly longer and had longer snouts when effects of variation in mass, snout width, body depth and age were accounted for. Discriminant function analysis (DFA) discriminated between sexes with 78% accuracy from 159 field collected specimens using standard length and snout length. Using coefficients from the DFA, the sex of 65 museum specimens was predicted to 85% accuracy. Sexually dimorphic standard length is probably related to gonad size differences between males and females. Reasons for snout length dimorphism are not apparent. This study demonstrates the existence of sexual dimorphism in spotted gar.