This study was carried out to evaluate the efficacy of a new oral bacteriotherapeutic drug in 63 children under 4 years old affected by infective diarrhoea or by extraintestinal infective pathology caused by oral antibiotic therapy. The patients were divided into three groups: the first and the second included subjects affected by acute diarrhoea enrolled in a comparative and controlled study; the third included subjects in chemotherapeutic treatment because suffering from infective extraintestinal pathologies, these patients were enrolled in a not controlled study. The first group underwent the rehydratant treatment for the acute enteritis together with the therapy with inactivated Lactobacillus acidophilus LB to value its antidiarrheic activity. To the second group (control group) was administered a no bacteriotherapeutic drug, while to the third group was administered the antibiotic therapy for extra-intestinal pathologies together with inactivated Lactobacillus acidophilus to avoid possible phenomena due to intestinal dysmicrobism. For all the patients included in the study, were reported; the number, the characteristics, the consistency of the motions and the description of the symptomatology during the treatment and daily. The greater part of the patients affected by the intestinal infective pathology subdued bacteriologic tests by coproculture. The obtained results showed a statistically significant clinical improvement of the first group patients compared with those of the second group, while those of the third group showed that the drug activity prevents the intestinal dysmicrobism affections due to the antibiotic therapy.