The objective of the study was to determine the patterns of use of antimicrobial drugs in the general population of the large, industrial city of Nagpur, India. Interviews of pharmacists and clients were carried out in a stratified, random sample of 34 pharmacies to determine beliefs and practices in prescribing and self-prescribing of antibiotics by complaint, choice of drug, dose, duration, cost, age and sex of the consumers. The study showed that drugs were dispensed without prescription despite prohibition by the Indian Pharmaceutical Act. Sales of antimicrobial drugs accounted for 17.5% of 511 purchases and 23.3% of expenditures for drugs. Proprietary brands of penicillins, co-trimoxazole and tetracyclines were dispensed most often (64.8%). The most common indications were upper respiratory, gastrointestinal and nonspecific complaints. The median number of units obtained was 5.0 (95% range 1-20), at a median cost of $0.50 per purchase, usually taken for less than five days. Repeat purchases were made without consulting a physician. Almost two thirds of purchases (63.9%) were for males, mainly under the age of ten years. Clients had poor knowledge of the indications, side effects, adverse reactions and appropriate duration of therapy. The dispenser viewed himself as a businessman rather than a professional and rarely offered unsolicited advice. Co-prescribing of 'tonics' added to costs and decreased the purchasing power for antimicrobial drugs. Most purchases of antimicrobial drugs in community pharmacies in Nagpur were for minor indications and were limited by the purchasing power of the consumers. It is doubtful that the choice of drug and the short duration of therapy would be effective for serious infections.(ABSTRACT TRUNCATED AT 250 WORDS)