A new oral macrolide, clarithromycin (TE-031, A-56268), was evaluated for its safety, efficacy and pharmacokinetics in 33 children. TE-031 was effective in all cases of mycoplasmal pneumonia, pneumococcal pneumonia, streptococcal pharyngitis, pertussis and Campylobacter gastroenteritis. The pharmacokinetic availability of TE-031 granule and tablets was much better than the older macrolides; serum half-lives of TE-031 averaged 3.2 +/- 0.25 hours (for the granule preparation). No clinical adverse reaction was encountered, but cases of transient mild elevation of the serum GPT (2 cases) and eosinophilia (2 cases) were encountered. From these preliminary data, TE-031 seems to have a place in the treatment of pediatric infectious diseases.