Clinical studies on SY5555 dry syrup, a new oral penem antibiotic, were carried out in the field of pediatrics. The following results were obtained. 1. SY5555 was administered to 10 children with various bacterial infections (2 patients with acute tonsillitis, 2 with acute bronchitis, 1 with pharyngitis, 2 with scarlet fever, 1 with pertussis and 2 with urinary tract infections). The overall clinical efficacy rate was 90%. 2. Side effects or abnormal laboratory test values were not observed except for loose stool in 1 and eosinophilia in 1.