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Song Sparrows (Melospiza melodia) provide one of North America's best examples of geographic variation in phenotype, with approximately 26 described subspecies recognized. However, researchers have found inconsistent signals when making comparisons between subspecies and genetic markers. We examined seven microsatellite loci from 576 Song Sparrows of 23 western North American populations representing 13 recognized subspecies. We assessed the level of concordance between microsatellite genotypes and subspecies. We found that in some, but not all, instances neutral genetic structure corresponded to recognized phenotypic structure. However, some populations not currently recognized as subspecies were found to be genetically differentiated from all other populations that are considered to be the same subspecies. We suggest that a combination of phenotypic characters, behavioral traits, and multiple loci be used when assessing geographic variation in birds, and that sampling should be conducted in more than one location within broadly distributed subspecies. Key words: geographic variation, Melospiza melodia, microsatellites, population genetics, subspecies. Melospiza melodia, con aproximadamente 25 especies descritas, es uno de los ejemplos mas conocidos en Norteamerica sobre variacion geografica fenotipica. Sin embargo, diferentes estudios han encontrado senales mixtas al hacer comparaciones entre subespecies y marcadores geneticos. Examinamos siete loci de microsatelites en 576 individuos de M. melodia de 23 poblaciones del occidente norteamericano, que representan a 13 subespecies actualmente reconocidas. Evaluamos el nivel de correspondencia entre los loci de microsatelites y las subespecies. Encontramos que, en algunos casos, pero no en todos, la estructura genetica neutral corresponde a la estructura fenotipica reconocida. Sin embargo, ciertas poblaciones no reconocidas actualmente como subespecies resultaron ser geneticamente diferentes de las demas poblaciones consideradas de la misma subespecie. Sugerimos usar una combinacion de caracteres fenotipicos, caracteres de comportamiento y multiples loci para evaluar la variacion geografica en las aves, y que los muestreos deben dirigirse a mas de una localidad para las subespecies ampliamente distribuidas.