The prevalence of betel quid chewing habit in Taiwan was surveyed in a group of Chinese people from Kaohsiung city and in a second group from the aboriginal inhabitants of South Taiwan. In all 1299 participants constituted Group 1 (85.2% response rate) and 827 Group 2 (70.1% response rate). People were interviewed in their homes in house-to-house survey, according to a structured questionnaire developed and evaluated by the authors. Of the Kaohsiung inhabitants covering all ages and both sexes, 6% was a current betel chewer and 4% was an ex-chewer, whereas 42% of the aborigines aged over 15 yr was a current chewer and 1% an ex-chewer. Lifetime prevalence was 10%. Betel chewing enjoys islandwide popularity among the 20 million inhabitants of Taiwan; the number of current and ex-users was estimated at 2.0 million (95% CI 1.6-2.4 million). The betel quid was prepared in two different ways. In one, used mainly by aborigines, fresh areca nut was simply wrapped with betel leaf and in another, popular mainly among Chinese, a lengthwise piece of betel fruit and lime paste was sandwiched between two halves of an areca nut. A high proportion of chewers was also a smoker and drinker, but tobacco was not found to be chewed together with betel quid. Consumption varied between 14 to 23 portions per day, with individual frequencies ranging widely from 1 to over 200 portions a day. A statistical analysis of sociodemographic factors showed that lesser educated older men, blue collar workers, smokers and drinkers were the likeliest betel chewers.