After a brief review of the data on cefotiam in the literature the report presents the results of microbiological research, a preliminary study into the drug's possible actions on phagocytosis and a polycentric clinical study of 93 cases of broncho-pleuro-pulmonary pathology and one sinusitis of the jaw. In vitro cefotiam was found to have an excellent inhibitory effect on gram positive and gram negative bacteria with MICs50 and 90 respectively 0.2 and 0.8 mcg/ml V. Staph. aureus, Str. pyogenes. E. Coli, K. pneumoniae and Pr. mirabilis. A dose-dependent increase in phagocytosis was noted. The clinical response was excellent with 90.43% (88/94) of the cases achieving clinical and radiological cure or very much improved. Cefotiam was very well tolerated with the appearance of 2/94 skin rashes (2.12%). The liver and kidney parameters showed no change at the end of treatment. No increase in enzymuria was noted during treatment with cefotiam.