OBJECTIVE: Resource utilization and cost effectiveness data were compared in patients taking 500mg OD (AM) levofloxacin (levo) with that of 500mg BID clarithromycin for up to 14 days. METHOD: Patients were eligible for this multicentre, double-blind study if they had signs and symptoms of acute sinusitis, including X-ray evidence. Clinical response was evaluated 2-5 days after completion of therapy and one month posttherapy. Utilization parameters were determined from the cost of drug, cost of the physician’s office or emergency room visit, and costs of concomitant medications. The total cost of resources and average cost per patient was calculated. The cost effectiveness ratio was determined by taking the average cost of product divided by the proportion of clinical success as assessed by investigator. The incremental cost effectiveness ratio is the mean cost per levo patient minus the mean cost per clarithromycin patient divided by the proportion of clinical success levo minus the proportion of clinical success clarithromycin. Cost minimization was calculated from the mean cost per levo patient minus the mean cost per clarithromycin patient. RESULTS: 191 patients had resource utilization data; 98 in the levo group and 93 in the clarithromycin group. The total cost of resources was $11,566.24 for levo and $12,635.14 for clarithromycin. Average cost per patient was $119.24 for levo and $135.86 for clarithromycin. The cost effectiveness ratio for levo was 1.3 and for clarithromycin 1.5. Since clinical success rates were similar a cost minimization analysis was performed. The result was 16.6. The incremental cost effectiveness ratio was -50.5. CONCLUSION: In patients with similar clinical success rates, this study shows that levo 500mg OD is more cost effective than 500mg BID clarithromycin.