Discriminant function analysis (DFA) has been used to sex many gull species. DFA has been used to determine the sex of Laughing Gulls (Larus atricilla) from Florida using three measurements. The function derived from the Florida population misidentified 40% of Laughing Gulls from a New York population. Laughing Gulls from New York were significantly smaller than those from Florida (P -< 0.004). A new discriminant function, based on bill, total body and wing lengths, that correctly classified the sex of 92% of gulls collected in New York was derived. These findings support past studies that suggest a discriminant function derived for one population cannot be applied with confidence to a different population of the same species.