We have compared the in-vitro bacteriostatic and bactericidal activity of ceftazidime against cephalothin-resistant Gram-negative bacteria, Haemophilus influenzae and Gram-positive bacteria. Comparison was made with cefaperazone, cefuroxime, moxalactam, cefotaxime, cefamandole, cefoxitin, cephalothin, cefazolin, azlocillin, carbenicillin, ticarcillin, ampicillin and oxacillin. In general ceftazidime was one of the most active compounds with low MIC and MBC values.