OBJECTIVE: To study the effect of a reduction in reimbursement of the cost of antibiotics on the prescribing pattern in primary care in Denmark. METHOD: We analyzed the general practitioners' prescriptions of antibiotics during 1993--96 in relation to a reduction in reimbursement on the basis of national health service data in the county of North Jutland (population 488 000). On 1 January 1996 the reimbursement for tetracyclines was withdrawn, and for other antibiotics reimbursement was reduced from 75% to 50%. RESULTS: The total consumption of all antibiotic groups increased steadily in the county until 1995, and in 1996 a decrease of 13% was seen. A very marked reduction was noticed immediately after 1 January 1996 for the more expensive broad-spectrum antibiotics. The use of tetracyclines dropped by 42% during the first 3 months of 1996 after withdrawal of reimbursement. CONCLUSIONS: It is reasonable to assume that the new reimbursement policy has initiated a reduction and caused a shift in general practitioners' prescribing of antibiotics. Thus a differential reimbursement policy might influence general practitioners' prescribing behavior towards antibiotics, with desirable ecological consequences.