Previous ecotoxicological studies have documented relationships between residues of various organochlorines (OCs) and immune status, carotenoid colors, and wing feather growth in different bird species. In this study, the density of white blood cells (WBC), carotenoid colors, and length of the same feathers on each wing were measured in breeding great black-backed gulls (Larus marinus) on the coast of northern Norway, and related to the blood residues of five OCs, including HCB (hexachlorobenzene), beta-HCH (beta-hexachlorocyclohexane), p,p'-DDE (p, p'-dichlorodiphenyldichloroethylene), oxychlordane, and polychlorinated biphenyl (PCB), in addition to SigmaOC. Neither, WBC density nor carotenoid colors were significantly related to blood residues of any of the OCs, suggesting that OC levels may have been too low to significantly affect these outcome parameters. However, in the colony where the OC concentrations were highest, there was a weak but significantly positive relationship between the probability of having different length of feathers on each wing and levels of PCB and SigmaOC, in males. Thus varying length of the wing primaries may reflect adverse impacts of OCs in great black-backed gulls. However, in gulls with moderate levels of OCs, it is probably not a sensitive indicator of progressing ecological impacts of OCs, since such adverse ecological relationships were found in the breeding colonies where there were no relationships between differences in wing feather lengths and OCs.