We studied the absorption and excretion as well as the clinical effect of rokitamycin (RKM, TMS-19-Q) dry syrup. The results we found are summarized as follows: 1. When 3 pediatric patients were medicated orally with a single dose of 10 mg/kg of the drug, its peak concentrations of 0.75 and 0.51 microgram/ml appeared in the blood in 30 minutes after administration in 2 patients, and of 0.21 microgram/ml in 1 hour in the other patient. At 4 hours after administration, its concentration in the blood was 0.07-0.08 microgram/ml in all of the patient, and at 6 hours, it was undetectable. T1/2 values were 1.05-2.08 hours. First 6-hour urinary recovery rates of the drug in the first 2 patients were 1.52 and 1.11%, respectively. 2. Twenty-four patients with 25 diseases were medicated with 7.14-12.5 mg/kg of the drug 3-4 times daily for 4-10 days. The patients consisted of 12 with tonsillitis, 7 with bronchitis, 3 with colitis, one each with Haemophilus influenzae pneumonia, mycoplasmal pneumonia, and pertussis. Clinical responses to the treatment were excellent in 7, good in 13, and poor in 5, with an efficacy rate of 80.0%. Bacteriologically, of 17 isolates whose changes were followed, 8 were eradicated, 1 decreased, and 8 remained unchanged, with an eradication rate of 47.1%. 3. No adverse reactions to the drug were observed in any of these patients, while abnormal laboratory test values observed were slight eosinophilia and also slight elevations of S-GOT and S-GPT in one of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)