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Long sequences of data on the incidence of cereal aphids from five European countries were analysed for evidence of density dependent processes occurring between years. Using a randomisation test (Pollard, Lakhani & Rotheray, 1987), density dependence was revealed in all (16) population censuses of Metopolophium dirhodum, 60% of Rhopalosiphumpadi censuses (10 of 17) but only 25% of Sitobion avenue population censuses (4 of 16). Correcting for density independent effects of weather revealed the existence of significant direct density dependence in some populations censuses where it was previously undetected. The implications of density dependence in cereal aphid populations are considered. study is to analyse in detail the year to year population dynamics of three species of cereal aphids for evidence of density dependence. Density dependence between seasonal peaks of aphid abundance, and interactions between weather and density dependence are also investigated.