14C-Rokitamycin (RKM) at the dose of 200 mg/kg was administered orally to fasted infant rats to study the absorption, distribution, metabolism and excretion in infant animals. The mean blood level of 14C-RKM reached its peak of 20.25 micrograms/ml in 30 minutes. The mean area under the curve was 93.23 micrograms.hr/ml. In vivo plasma protein binding rates of 14C-RKM were about 30% in both infant and adult rats. 14C-RKM was distributed at high concentrations into liver, kidney, lung, spleen, pancreas, bone marrow, submaxillary gland and some other tissues. Major metabolites detected in plasma, urine and bile were 10"-OH-RKM, leucomycin A7, leucomycin V and 14-OH-leucomycin V. In excretion studies, about 97% of the administered radioactivity was recovered in urine and feces within 144 hours. After intraduodenal administration to rats with cannulated bile ducts, 7.42% and 25.66% of the radioactivity were excreted within 24 hours in the urine and bile, respectively.