Recurrent lower respiratory tract symptoms are common and disabling in childhood, but little is known of their natural history and relationship to asthma. We report a 12-month longitudinal study designed to determine the influence of atopy on respiratory symptoms and bronchial responsiveness in 7- and 8-yr-old children. A postal questionnaire inquiring into the presence of respiratory symptoms was sent to 3,698 children aged 7 and 8 yr. Those reporting either current wheeze (14.8%) or current cough in the absence of wheeze (12.8%) were randomized, and a sample was invited to attend for skin testing. The following groups of symptomatic children entered the longitudinal study: 48 atopic children with cough, 48 atopic children with wheeze, 48 nonatopic children with cough, and 48 nonatopic children with wheeze. All children recorded twice daily the best of three peak expiratory flow (PEF) measurements and completed a 10-point symptom score card, each day for 1 yr. They also recorded all treatment taken and made a note of relevant life events. Each child was seen monthly for general assessment and for measurement of methacholine bronchial responsiveness. Despite the arduous nature of the study 183 of the 192 children (95.3%) successfully completed the 12 months of observation. Symptom groups were compared with regard to FEV1, bronchial responsiveness, symptom chronicity and severity, and diurnal and day-to-day variation in PEF. Atopy was associated with a lower FEV1, increased prevalence of bronchial hyperresponsiveness, greater within-day and between-day variation in PEF, and greater severity of respiratory symptoms compared with the absence of atopy. Wheeze was associated with lower FEV1, increased prevalence of bronchial hyperresponsiveness, greater within-day and between-day variation in PEF1 and greater severity of respiratory symptoms compared with cough [corrected].