The aim of the study was to evaluate the influence of the month of birth on the development of atopic disease and the rate of sensitization to common environmental allergens in Greece. Analysis of the month of birth of 1755 individuals with atopic disease (asthma, rhinitis, atopic dermatitis), out of whom 771 had positive skin tests/RAST to Dermatophagoides pteronyssinus and mixed grasses, in comparison to total live births (2,877,733) in Greece during 1968-88, was performed and showed significant correlation (p < 0.001) between month of birth and development of atopic disease in general. Months of birth May to August correlated best with bronchial asthma (p < 0.05) and rhinitis (p < 0.05), and July to August with atopic dermatitis (p < 0.05). Significantly greater than the expected frequency was found for D. pteronyssinus sensitivity for months of birth May to August (p < 0.01), for mixed grass pollen March to August (p < 0.01), and for Olea europaea pollen mainly March (p < 0.05). Our results indicate that in Greece high-risk birth months for development of atopy are May to August, whereas for sensitization to common aeroallergens they are March for O. europaea, March to August for mixed grasses, and May to August for D. pteronyssinus.