Cefprozil is a new orally active cephalosporin which is undergoing in vitro and in vivo evaluations. Using the standard agar dilution method we compared the in vitro activity of this drug with other oral cephalosporins and ciprofloxacin against 637 recent clinical isolates from the Kaohsiung Veterans General Hospital, Taiwan. Against Escherichia coli and Klebsiella pneumoniae, cefprozil showed good activity, inhibiting over 80% of these isolates at 8 mg/l. Like other oral drugs of its class, it had little activity against Pseudomonas aeruginosa and Acinetobacter spp. Against Haemophilus influenzae, irrespective of β-lactamase production, its activity was similar to comparable drugs. Against methicillin-susceptible Staphylococcus aureus, cefprozil showed high activity, inhibiting 90% of these isolates at 4 mg/l, whereas against methicillin-resistant S. aureus, its activity was higher than that of other oral cephalosporins tested and was similar to that of ciprofloxacin. Of enterococci tested, 57.7% were inhibited by 8 mg/l of cefprozil. Against β-hemolytic streptococci, its activity was superior to all other drugs tested. The results of this in vitro study indicate that oral administration of cefprozil might be efficacious in the treatment of community-acquired cutaneous, respiratory and urinary tract infections.