We tested the hypothesis that larger individuals in a temperate fish population emerge from winter in better energetic condition than do smaller individuals. We sampled adult male bluegillsLepomis macrochirusin Lake Opinicon, Ontario, after spring ice break and just before active feeding began. By extracting neutral and membrane-bound polar lipids. we estimated the energetic condition of each individual. We found that both the mass of lipids and the lipids per gram of body weight were significantly and positively correlated with body size. These results are attributed to the allometric relationships between body size and energy reserves and between body size and metabolic rate. Body size, therefore, profoundly affects energetic state, which may explain why individuals of different size vary in their reproductive behavior and survivorship.