Rokitamycin dry syrup (RKM), a new macrolide antibiotic preparation, was evaluated for its safety, efficacy and pharmacokinetics in 19 children. RKM was effective in mycoplasmal pneumonia, Chlamydia trachomatis pneumonitis and Campylobacter gastroenteritis. Efficacies of RKM in streptococcal pharyngitis and Haemophilus influenzae pneumonia, however, were insufficient. Pharmacokinetic observations seemed to indicate that RKM achieved higher blood concentrations than older macrolides, but a large individual variation was observed. Diarrhea which was the only type of side effect observed in our cases, was encountered in 2 of 17 evaluable cases. From these data, RKM seems to have a place in the treatment of pediatric infectious diseases.