Because Campylobacter jejuni is most frequently identified as a causative organism of bacterial enteritis in pediatrics, a study was done to evaluate the clinical efficacy against Campylobacter enteritis and the safety of a macrolide antibiotic, rokitamycin (RKM). In case of acute enteritis, RKM was used in a form of dry syrup at a dose level of approximately 30 mg (in potency)/kg body weight and its efficacy and safety were compared to those of fosfomycin (FOM) dry syrup which is currently in use at a dose level of 60 mg (in potency)/kg. Both drugs were administered, as a rule, in 3 divided daily dose (RKM before meal and FOM after meal) for 5 consecutive days. Comparisons of the drugs were made using a well-controlled method. Obtained results are summarized as follows. 1. No significant differences in background factors of the 2 drug groups were apparent, hence it was deemed that no obstacles existed in making comparative studies of the 2 groups with regard to their efficacies and safeties. 2. Overall efficacy rate against Campylobacter enteritis was 100% in the RKM group with a rate of excellent efficacy of 91.3% and the former was 94.4% in the FOM group with the latter of 72.2%. Though the RKM group apparently showed higher rates by 5.6% and 19.1%, respectively, for overall and excellent efficacies, they were not statistically significant as both drugs showed good efficacies. When acute cases of enteritis other than those caused by Campylobacter were included in the analysis, overall efficacy rates and rates of excellent efficacy were, respectively, 97.6% and 85.7% for the RKM group and 88.6% and 68.2% for the FOM group, thus RKM showed higher efficacy rates by 9.0% and 17.5%, respectively. These differences were deemed statistically significant using the U-test. 3. Numbers of days required for most of the major symptoms to subside were 3 days or less for the group for which RKM was used against Campylobacter enteritis. Similar results were observed for the FOM group also. In cases of acute enteritis due to other causes than Campylobacter, slower recoveries were observed for both the RKM and the FOM groups than in Campylobacter enteritis cases, with the latter group slower than the former. In cases of puruloid stool, the recovery in the RKM group was significantly faster by U-test than the FOM group, and a similar trend was observed overall. 4. Bacteriologically, the eradication rate of Campylobacter in the RKM group was very good at 91.3% with the FOM group showing a rate of 78.9%.(ABSTRACT TRUNCATED AT 400 WORDS)