Hemoglobin polymorphism in all 10 genera of emydid turtles was examined by isoelectric focusing. Two major (highly concentrated) forms of hemoglobin were revealed in all turtles examined. Cathodal electromorphic bands of hemoglobin (Hb A) demonstrated isoelectric points (pI) 7.6–8.3, and anodal bands (Hb D) demonstrated isoelectric points 5.2–6.1. The most common forms of Hb A (pI 8.3) and Hb D (pI 6.0) were shared by Pseudemys, Graptemys, Malaclemys, and Trachemys. Relatively little intrageneric variation was observed except among species of Clemmys, which lends support to the hypothesis that the genus Clemmys is not monophyletic. Ontogenetic hemoglobin polymorphism was observed in Trachemys scripta elegans and Trachemys scripta troostii.