Because there was no agreed operational definition of asthma, an attempt was made to identify, within the community, individuals with a cluster of features which would include those commonly found in asthmatics. We have therefore looked at the prevalencee of some respiratory symptoms and studied in more detail a subgroup of patients looking in particular at bronchial hyperreactivity and its relation to respiratory symptoms. The study comprised two surveys conducted in one area of Southampton, each survey was designed in two phases. The first survey Phase I: Questionnaires were sent to a systematic sample of 2149 subjeects. A response rate of 74% was obtained. 30% of the respondents had shortness of breath, 11% had morning tightness, 6% had nocturnal dysponoea, 27% had wheezing and 12% had productive cough. Phase II: because the prevalence of shortness of breath and wheeze were high and the interrelation between both symptoms four groups were selected at random. Group I subjects with SOB; Group II subjects with wheeze; Group III subjects with both SOB and wheeze; Group IV subjects with neither SOB nor wheeze. Spirometry and histamine challenge were carried out on 102 subjects who attended the department. Bronchial hyperreactivity (BRR) was defined by relating reactivity to specific symptoms,the symptomatic counterpart to BUR 'bronchial irritability'(BI) was defined. On defining ERR and BI a group of subjects with a cluster of features was identified; these features were: BI and/or nocturnal dyspnoea (ND)and/or morning tightness(MT)for more than one hour and BHR. these features constituted by definition a syndrome which was labelled ~SHABI~.The second survey: designed to shed light on this syndrome. Phase I: A simplified version of the questionnaire sent to a systematic sample of 2000 subjects. The response rate was 80%. There were no significant difference between the prevalence of respiratory symptoms in both surveys. Phase II Four groups were selected; Group I ~SHABI~ all subject with one or more of the following: BI, ND, MT > lhr. Group II all subjects with MT < lhr. Group III: random sample from subjects with SOB+wheez. Group IV random sample from subjects with no respiratory symptoms. Spirometry and/or bronchial challenge were carried out on 105 subjects who attended the department. All subjects with ~SHABI~ had BHR. There was positive correlation between FEV1% predicted and PC20 for ~SHABI~ and Group II. All those diagnosed by General Practioners as having asthma were contained in ~SHABI~. The prevalence of ~SHABI~ was 5.5% in men and 4.8% in women between the age of 19-70 years.