Studies on the elemental composition of bluegills and other freshwater fish revealed that fish differ in concentrations of calcium, magnesium, potassium, sodium, nitrogen, phosphorus, sulfur, and ash depending upon species, size, and collecting site. For rigorous considerations of the elemental composition of fish in a body of water, fish of different species and sizes must be collected and analyzed. Nevertheless, for many ecological purposes, the variation in elemental concentrations was not too large to prevent generalizations from data presented in this study.