A double blind, randomized clinical trial involving 214 children, ages 6 months to 12 years, compared the safety and effectiveness of the new carbacephem loracarbef and the cephalosporin cefaclor for the treatment of skin and skin structure infections. The two agents were given primarily as oral suspensions. Dosages were 15 mg/kg/day in two divided doses for loracarbef and 20 mg/kg/day in three divided doses for cefaclor. Assessment 72 hours after completion of the 7-day course of treatment indicated a favorable clinical response plus eradication of the pretherapy pathogen in 97.3% of the 74 loracarbef-treated patients eligible for evaluation and 92.3% of 78 evaluable cefaclor-treated patients. Favorable response rates at a second posttreatment visit 10 to 14 days after the end of therapy were 95.6% in 68 evaluable loracarbef-treated patients and 86.2% in 65 treated with cefaclor. The incidence of adverse reactions, including gastrointestinal effects, was low in both groups. No statistical difference in clinical or bacteriologic efficacy or safety was detected between patients treated with loracarbef and cefaclor.