Data cover the patterns of heroin abuse, abuser sociodemographic characteristics, and heroin-related disability. From 1971 to 1981 only four heroin addicts, all foreigners, were admitted to the unit. The first two heroin addicts from Sri Lanka were hospitalized in the unit in 1982, and the number increased to 92 in 1983. Most addicts treated in the study period inhaled heroin, and the average amount consumed was 340 mg per day. The majority had used heroin for less than 1 year, and 9 percent had used it for more than 2 years. All the addicts were males. Only 6 percent were older than 34 years; 5 percent were unemployed at the time they started using heroin; 67 percent were single; and 93 percent had left school before the 10th grade. Two ethnic groups -- Moors and Burghers -- were overrepresented compared with the proportion of these groups in the national population. The majority of the employed addicts (70 percent) reported that heroin addiction had interfered with their ability to work. The availability of heroin at a low price in neighboring countries, the growth of the tourist industry, and the rapid changes in the socioeconomic conditions of the people may be contributing to the spread of heroin abuse in Sri Lanka. 9 references. (Author abstract modified)