We examined sexual dimorphism of Dovekie (Alle alle) from the breeding colony in Hornsund (south Spitsbergen). Each bird was sexed using DNA extracted from blood. Body morphometrics including flattened wing, head-bill, tarsus length, bill width and body mass were recorded in 331 birds caught during the breeding season in 2003-2006. Analysis of measurements of mated pairs showed that males are usually bigger than females in case of head-bill length, bill width and body mass. Only head-bill length was significantly correlated within a pair (r₆₉ = 0.354, P < 0.005). A forward stepwise discriminant function analysis (DFA) was used to evaluate sexual size dimorphism in Dovekie. The first function, applied to 4 measurements, identified head-bill length and bill width as the best measurements for sexing and correctly classified 70% of our sample (but only 38% better than chance). The second function, which was applied to only 3 parameters (excluding bill width), identified head-bill length as the best measurement for sexing and correctly classified 65% of our sample (30% better than chance). In Dovekie, a species having a high degree of overlap between the sexes, discriminant function should be used with caution. It is recommended that a combination of morphometrics, behavior observation and genetic analysis be used to obtain the highest accuracy in sexing individuals correctly.