Lipid and fatty acid contents of fillets (with skin) of Atlantic croakersMicropogonias undulatus, striped mulletMugil cephalus, and summer flounderParalichthys dentatuswere determined for three harvest dates over a 1-year period. In striped mullet and Atlantic croakers, total lipid increased significantly (P≤ 0.05) in late summer (from 21.72 to 31.78% and 12.68 to 31.94% of dry weight, respectively). No significant change in total lipid content was noted in the leaner summer flounder (9.38–9.87%). However, polyunsaturated fatty acid (PUFA) content of fillets of summer flounder varied significantly (P≤ 0.05), ranging from low levels in June and August (6.24 and 3.33% of dry weight, respectively) to much higher levels (17.32%) in January. The difference in PUFA content of fillets was due mainly to a significant increase in docosahexaenoic acid (22: 6n3). The PUFA content of Atlantic croakers (22:6n3) also increased significantly (from 3.19 to 6.16%) from August to January, but the PUFA content of striped mullet did not change significantly. These results indicate that generalizations cannot easily be made concerning the lipid and fatty acid composition offish. We speculate that for some species (e.g., Atlantic croaker and striped mullet), high food availability linked with preparation for spawning is a primary determinant of lipid content, but for other fish (e.g., summer flounder), changes of PUFA content in response to temperature change are more important.