A study was set up to examine the prevalence and management of asthma symptoms in a London inner city general practice. All case records were examined and evidence of past or currently active asthma or wheezing illness was identified in 1032 out of 11,148 records (9.3%). This gave a cumulative prevalence of asthma or wheezing illness of 7.2% among adults and 19.5% among children aged 15 years or under. These figures are consistent with previous estimates of prevalence in the UK published since the mid 1960s. In 92.5% of cases in which information was available, the initial diagnosis of asthma or decision to prescribe a bronchodilator was made in primary care. Only nine cases (0.9%) had evidence of recurrent wheezing without the benefit of bronchodilator therapy at any time. There was significant delay in diagnosis in children under five years compared with older children or adults. There was a significant association between a formal diagnosis of 'asthma' in the case notes and the inclination of general practitioners to monitor peak expiratory flow or offer inhaled bronchodilator or corticosteroid therapy. Of 111 asthmatics (83 adults and 28 children aged five to 15 years) with previously 'severe' disease who sought medical advice for their asthma over a 12 month period, 91.6% of adults and 92.9% of children received bronchodilator therapy; nevertheless, only 47.0% of adults and 14.3% of children received inhaled corticosteroids and only 12.0% of adults and 28.0% of children received inhaled cromoglycate. Only 59.0% of adults and 46.4% of children had at least one measurement of peak expiratory flow during the 12 months.(ABSTRACT TRUNCATED AT 250 WORDS)