Levels of eight PCB congeners (IUPAC 8, 20, 28, 52, 101, 118, 138, 180) and 13 organochlorine pesticides (alpha -BHC, beta -BHC, lindane ( gamma -BHC), heptachlor, heptachlor epoxide, aldrin, dieldrin, endrin, 2,4 ' -DDT, 2,4 ' -DDD, 4,4 ' -DDT, 4,4 ' -DDD, 4,4 ' -DDE) were measured in unhatched Audouin gull eggs from Aegean Sea (northeastern Mediterranean) colonies in 1997 and 1998, Levels of more persistent congeners 138, 180 and in some colonies 118, predominated among PCBs, Between years significant differences were found in the levels of a variety of contaminants in the same regional colonies (Lipsos, Agathonisi, and Fourni) attributable to temporal changes in diet. Within years differences were limited (1997: PCB congeners 52, 118, 180, heptachlor and 4,4 ' -DDD; 1998: PCB congener 8 and heptachlor epoxide) which in combination with cluster analysis suggest a temporal rather than spatial pattern of pollution in the Aegean Sea. Maximum median levels of five PCB congeners, total PCBs and eight organochlorine pesticides were found in the Agathonisi and Fourni colonies suggesting an elevated nearby pollution probably from the polluted Menderez River. Levels of all contaminants were too low to have any adverse reproductive effects on the Audouin's gull of the Aegean colonies. (C) 2001 Elsevier Science Ltd, All rights reserved.