Four-hundred-and-forty-six electrophoretic patterns of bluegill (Lepomis macrochirus) serum proteins were analyzed to determine the condition of fish when sampled from ponds with different population densities. It was extremely difficult to rank ponds according to population density by using electrophoresis because of intraspecific variation. This variation was attributed to sex, maturity, season, and ponds, but not all the variation was accounted for in these variables.