A pharmacoeconomic study of 15 antibiotics available in Barbados was performed. The antibiotics studied were amoxycillin/clavulanate, ampicillin, ampicillin/sulbactam, cefazolin, cefotaxime, ceftazidime, ceftriaxone, clindamycin, cloxacillin, cotrimoxazole, gentamicin, imipenem, metronidazole, piperacillin, piperacillin/tazobactam, and vancomycin. The costs of use of these compounds were calculated for a five-day course using a formula comprising eight categories: antibiotic purchase cost, maintenance of intravenous access, drug delivery cost, drug monitoring cost, dose readjustment, general monitoring cost, 'sharps' disposal cost and adverse effects. The costs of adverse effects were not included in this study due to lack of accurate data. The total cost of antibiotic use (in U.S. dollars) ranged from $42.52 to $463.73 per five-day course. Generic compounds were less expensive ($45.52 - $98.23) than brand-name compounds ($106.18 - $106.18 - $463.73). Antibiotic purchase costs accounted for proportions of total costs ranging from 7 to 93%. Non-drug costs represented a much greater proportion of total costs of generic compounds. For most compounds the non-drug costs were related to the frequency of dosing, but for gentamicin the non-drug costs were relatively higher because of the need for monitoring of serum gentamicin levels. Efficacy and freedom from side-effects will remain the most important determinants in the choice of antibiotic therapy. However, pharmacoeconomic analyses can provide prescribers with the information required to make cost-effective choices for treatment of their patients.