The prevalence of asthma and eczema in children between 3 and 10 years of age living in Hong Kong was determined by a questionnaire survey administered to the parents of 535 children in 1989. The prevalence of asthma was 6.0% (95% confidence limit (CI) 4.0-8.0%) and the prevalence of eczema 6.8% (95% CI 4.6-9.0%). Age, sex, parental smoking and breast feeding in early life did not show significant associations with asthma. However, four different measures were associated with the prevalence of asthma: the presence of eczema, high serum IgE level, high number of upper respiratory infections and a relatively high family income, with odds ratios of 7.6, 4.9, 4.5 and 2.7, respectively.