In order to determine the prevalence of asthma, allergy and atopy in southern China and the relative importance of atopy and parental history in predicting asthma and allergic diseases, we carried out a cross-sectional study on 737 secondary school students aged 12-20(492 boys, 245 girls; mean age = 16.4 years, so = 1.8 years) in the city of San Bu, Guangdong, China. Standard questionnaires on respiratory and allergic symptoms were distributed for completion by parents with an overall response of 98.6%. Skin-prick tests to common aeroallergens were performed on 647 subjects (87.8%) to determine atopic status. The prevalence (and 95% CI) of a history of hay fever, eczema, wheeze or asthma ever and wheeze in past 12 months were 1.6% (0.7-2.5), 10.4% (8.2-12.6), 1.9% (0.9-1.9) and 1.1% (0.3-1.9) respectively. Forty-nine per cent (45.2-52.9) of students had one or more positive skin tests to common aeroallergens. Amongst atopic subjects, 87.3% reacted to house dust mite (Dermatophagoides pteronyssinus) and 73.3% to cockroach. There was a close association between the degree of atopy and the prevalence of a history of wheeze (P < 0.05) but not with hay fever or eczema. After adjusting for age and sex, parental histories of hay fever, eczema and wheeze were strongly associated with the respective symptoms in the subjects (OR = 17.4 (3.2-93.9) for hay fever, 27.4 (12.7-59.0) for eczema, 79.4 (21.9-288.4) for wheeze). It is concluded that respiratory and allergic symptoms were uncommon in Chinese school students despite a high prevalence of atopy, and that parental history is more important in predicting asthma and allergy than atopy.