We studied the pharmacokinetics of a new cephem antibiotic, S-1108, in patients with impaired kidney functions. Serum and urinary levels of S-1006 were determined after oral administration of S-1108 at 150 mg to 9 patients with renal dysfunction. In patients with severe renal impairment, high serum levels were maintained over long periods of time. Urinary excretion rates of S-1006 were lower as degrees of kidney failure were severer. S-1108 was administered to treat 27 patients with respiratory tract infections, and its clinical efficacy and safety were evaluated. The clinical efficacies were good in 26 patients, but poor in 1, yielding an efficacy rate of 96.3%. As to adverse reactions; diarrhea was observed in one case. Laboratory tests revealed elevated GOT and GPT in 1, and elevated gamma-GTP in another. These abnormalities, however, were slight and no severe side effects were caused by the drug.