The clinical efficacy and safety of cefixime (CFIX), a new oral cephalosporin, were compared with those of cefroxadine (CXD) in patients suffering from acute lacunar tonsillitis in a double blind study. Two hundred and fifty two patients were given each orally 100 mg of CFIX b.i.d. or 250 mg of CXD t.i.d. for, in principle, 7 days. Number of patients evaluated for clinical efficacy was 202 (103 treated with CFIX and 99 treated with CXD). As for the backgrounds of patients, more severe cases were found in the CFIX group than in the CXD group (P less than 0.01). Efficacy rates evaluated by individual doctors were 88.3% in the CFIX group and 91.9% in the CXD group. There was no significant difference between the 2 groups. Efficacy rates on the third day after the initiation of treatment evaluated by the committee were 40.8% in the CFIX group and 47.9% in the CXD group with no significant difference. Efficacy rate on the 7th day, however, was 79.8% in the CFIX group and 93.4% in the CXD group, showing a significant difference (P less than 0.05). Bacteriological effectiveness were satisfactory for both groups with eradication rates of 93.4% for the CFIX and 96.9% for the CXD group. Number of patients evaluated for safety was 226 (110 treated with CFIX and 116 treated with CXD). No significant difference was observed between the 2 drug groups in incidences of side effects; gastrointestinal disturbances or rashes were noted in 6 patients (5.5%) of the CFIX group and in 5 patients (4.3%) of the CXD group. As for the abnormal laboratory findings, elevation of GOT & GPT was observed in 1 patients of the CFIX group. From these results, it was concluded that 100 mg b.i.d. of CFIX was as useful as 250 mg t.i.d. of CXD in the treatment of acute lacunar tonsillitis.