A questionnaire was sent to a random sample of adults in eight locations throughout Britain, to investigate the prevalence of snoring, asthma and sleep complaints in community-based British adult. Of the 1,478 respondents (831 females, 647 males; mean +/- SD age 45 +/- 18 yrs), 37% reported snoring at least occasionally, and 11% reported snoring on at least four nights per week (frequent snorers). Frequent snorers reported spending less time asleep at night, falling asleep accidentally during the day more often, taking planned daytime naps, and falling asleep whilst driving or operating machinery more often than the other respondent. Using ordinal logistic regression analysis to allow for the age and sex of the respondents, both accidental daytime sleep and planned daytime naps were commoner in frequent snorers than other respondents. Six percent of all respondents and 6% of those aged under 40 yrs reported that they had asthma (asthmatics). Seven percent of respondents aged less than 40 yrs reported wheezing on three or more occasions per year, and had been prescribed oral or inhaled bronchodilators (young wheezers). More than 80% of the asthmatic respondents of all ages, and young wheezers, reported waking at night with wheeze at least occasionally, and more than 30% of each group reported this symptom frequently. A larger proportion of asthmatics and young wheezers reported that their night-time sleep was unrefreshing, and that they had too little sleep at night than the other respondents.(ABSTRACT TRUNCATED AT 250 WORDS)