Sale of modern medicines by untrained peddlers, general merchants, and other drug sellers is common throughout the developing world. Drug sellers operating in the 'informal sector' are often the first source of health care outside the home. Reasons given by patients for using private drug sellers include expediency, convenience, efficacy of the medicines, dependability of supply, and reasonable cost. At the same time, self-medication through private drug sellers can be ineffective, wasteful, and at times distinctly harmful. Regulatory approaches to controlling drug selling in the informal sector, widely endorsed on paper through national drug control legislation, require a cadre of professional regulatory staff and enforcement mechanisms which are too often beyond the current economic and political reach of countries. In Nepal, where rugged terrain has limited infrastructure development, the doctor to population ratio is 1:23,000, utilization of government health services averages only 0.2 visits per person per year. Retail drug outlets outnumber health posts and health centers by a ratio of 4:1 and private drug sellers often offer the only access to modern medicine for much of the population. Community surveys have found that drug retailers are very often the first and only source of health care outside the home. Given the importance of retail drug outlets and the lack of trained pharmacists, the Department of Drug Administration in 1981 established a 45-hr course for drug retailers which emphasized practical training as well as formal teaching on pharmacology, ethics, storage of drugs, and legal issues. By the end of 1989, 4096 drug retailers had graduated from the course. Still run by the Ministry of Health Department of Drug Administration, the course has proven to be administratively feasible and has been quite popular with drug retailers. Initial reservations expressed by doctors and some pharmacists were soon overcome, and the course is now well accepted by professional groups. Because the course is offered in different locations, geographic coverage has also been very good despite Nepal's logistic constraints. The operating cost of the course averages about U.S. $18 per trainee. Informal evaluations have resulted in plans for refresher training more narrowly focused on safe dispensing and appropriate referral for a limited number of important public health problems. Since 50-90% of pharmaceutical expenditures typically pass through the informal private sector in developing countries, it is suggested that other countries consider focused drug retailer training as a response to the problems of manpower shortages and drug dispensing by unqualified staff.