The survival of Africanized honey bees,Apis melliferaL., in temperate regions was evaluated in Germany during the 1988–1989 winter. Africanized, local European, and Africanized × European colonies were started by queen introductions on 5 August, and all surviving colonies were depopulated on 21 February. Five of nine Africanized colonies had died by the end of the experiment, whereas all eight European and all five Africanized × European colonies survived. Brood production of the three genotypes declined from 18 August until 13 November with significant differences on two of the seven measurement dates. Brood areas were not different among surviving colonies that had resumed brood production by 21 February. Changes in total colony weights through time were not different. Significant differences were found in the rates of colony weight loss (kilograms total weight/average kilograms of adult bees∗time)and in final adult population size. The higher attrition of worker populations and the higher mortality of Africanized colonies suggest a possible reduction of their adverse effect as their range expands northward to temperate areas in the United States. The intermediate values for all characters in the Africanized × European colonies suggest that genes underlying overwintering characters are additive. This additivity will permit different levels of hybridization for different ecological zones, thus complicating predictions about absolute climatic limits.