Early feeding is generally recommended for children with acute diarrhea. The concentration at which the milk should be given to children weaned at an early age remains a matter of debate. The aim of the study was therefore to evaluate the role of milk dilution in the first 24 hours on the outcome of diarrhea. Sixty-nine well nourished and weaned children, aged 1 to 9 months and with moderate watery acute diarrhea were included after oral rehydration therapy (ORT) in a randomised controlled study to receive either half-strength (diluted group) or full strength (undiluted group) milk. Both groups displayed the same clinical characteristics except for the weight. The outcome of the diarrhea until cessation was the same in the 2 groups. No failure requiring a specific treatment was observed. The duration of diarrhea and the total stool output were not statistically different in the 2 groups, i.e. 39 +/- 7 hrs in diluted vs 47 +/- 8 in undiluted, and 883 +/- 205 g in diluted vs 924 +/- 161 g in undiluted. These results are strengthened by the lack of significant differences in the weight gain, the number and volume of vomiting, the volume of ORT and milk intake. However, the energy intake was significantly higher in the group receiving full strength milk. These results suggest that there is no immediate clinical advantage to dilute the milk in the first 24 hours of feeding well nourished children with moderate acute watery diarrhea, if early feeding is associated with the ORT recommended by the WHO.