Analysis of color and structural variation in Costa Rican populations of the frog Eleutherodactylus bransfordii delineates three basic dorsal patterns, four distinct types of ridging patterns, and ten modifying color characters, that may be superimposed at random on the back patterns. The animals can be grouped into four distinct morphs based upon the color and ridging characters. Morph I includes frogs with uniform back color and scattered ridging, Morph II with mottled back color and scattered ridging, Morph III with uniform back color and V-shaped or hourglass ridging, and Morph IV with dorsolateral stripes, and dorsolateral, parallel ridging. The morphs are not expressions of sexual dimorphism. Frequencies of morphs are significantly different between nine populations with large samples. No obvious correlation with bioclimate, altitude, or vegetation is suggested by morph frequency differences. It appears that uniform-mottled-dorsolateral stripes are probably allelic expressions of one gene, with uniform representing the heterozygous condition. Ridging appears to be controlled by three allelic expressions of one gene, with parallel ridging a homozygous recessive, V-shaped and hourglass another homozygous recessive, and scattered ridging dominant over the other alleles.