Cefmetazole (CMZ), a new cephamycin preparation, has been investigated to give following results. 1) Pharmacokinetics: Serum and tonsil concentration of CMZ were determined by micropore method in humans. The mean concentrations in 5 cases about 30 minutes after administration of 0.5--1.0 g intravenously were 55.4 micrograms/ml in serum, 21.7 micrograms/g in tonsil. 2) CLINICAL STUDIES: Seventy-one patients with ear, nose and throat infections were treated with CMZ receiving 1 to 6 g per day intravenously (one shot and drip infusion). Thirty-eight of 70 patients were cured excellent, 19 were good, 8 were fair and 6 were failure and effective rate was 80.3%. Adverse reaction was observed in 4 cases. Three cases showed exanthema and 1 case showed fever elevation.