A new macrolide antibiotic preparation, TMS-19-Q.O tablet, was used to investigate the efficacy in the treatment of patients with respiratory tract infection, and the results obtained were as follows: Three hundred and seven cases were included in this report, and overall efficacy rate was 76.2%. Especially high clinical effect (86.0%) was observed in the treatment of patients with pneumonia including mycoplasmal pneumonia. Bacteriological effect was 87.5% in 51 cases identified as single infection of Gram-positive cocci and was 48.0% in 34 cases Gram-negative rods infection. Side effects were observed in 11 cases (3.50%): gastrointestinal disorder in 8, eruption in 2 and other in 1. Abnormality in laboratory tests was observed in 23 cases, hepatic disorder in 13, renal disorder in 3 and other laboratory tests in 7. It was considered from the results of clinical and bacteriological efficacy in different dose study that dose of TMS-19-Q should be 600 mg.