OBJECTIVE: To analyze hospital treatment of infants with acute gastroenteritis, especially the variations in modes of rehydration, hospitalization rates and lengths of stay, related to paediatrician permanency with a short-stay observation unit at their disposal. METHODS: This prospective multicentric study during two rotavirus epidemic periods included 1,187 infants (mean age 10 +/- 6 months) with acute gastroenteritis resulting or not in dehydration. During the first period, 12 volunteer hospitals were included. During the second period, we compared six (among the 12) hospitals where infants were admitted in emergency care or pediatric units without pediatric 24-h permanency, with a pediatric emergency care unit having pediatric permanency with a short-stay observation unit. RESULTS: During the first period, 32% were dehydrated and 6% had hypovolemic shock on admission. The hospitalization rate was 81%. Only 19% of dehydrated infants had exclusively oral rehydration, and 19% of normohydrated infants had intravenous rehydration. During the second period, the hospitalization rate was 42% in the pediatric emergency care unit (28% in the short-stay unit and 14% in hospitalization units) versus 77% in the six hospitals. In the pediatric emergency care unit as compared to the six hospitals, there were a reduction of 65% of hospitalization days, 58% of intravenous accesses, and 66% of laboratory tests. CONCLUSION: Our findings suggest that a paediatric permanency with a short-stay observation unit at their disposal improves quality of treatment and is cost-effective.