Background: In Bolivia there are few probiotic preparations available in the market, practically without alternatives to the use of freeze-dried products. An alternative used as a good alternative in other parts of the world is yogurt with a probiotic strain added. In this study we report the use of a locally prepared yogurt with a lyophilized probiotic added. Methods: This is randomized, double-blind and controlled clinical trial in children hospitalized with acute diarrhoea carried out at the Paediatric Centre Albina Pati?o in Cochabamba, Bolivia with children 10 to 35 months participating. Children were randomly assigned to receive an oral rehydration solution and Saccharomyces boulardii (positive control) or the same solution plus yogurt preparation containing Lactobacillus rhamnosus (yogurt group). The primary outcome was the duration of diarrhoea. Secondary outcomes were the duration of fever, vomiting and hospitalization. Results: Of the 74 children incorporated 42 completed the protocol; baseline characteristics were similar in both groups. The median duration of diarrhoea was similar in children who received yogurt (71 hours) and controls (79 hours) (p = 0.3). The mean duration of fever was also similar in both groups: S. boulardii (24 hours) or yogurt (11 hours) (p = 1.02), as was the duration of vomiting: 17 hours vs. 32 hours in the control group (p = 0.37). A significant difference in the numbers of daily bowel movements was observed in the third day, the probiotic group was lower (p =< 0.01). There was no effect on the duration of hospitalization (p = 0.26). Conclusions: The use of a yogurt containing L. rhamnosus has an effect comparable to S. boulardii. Introduction of yoghurt with a probiotic in the diet of patients hospitalized with acute diarrhoea may help reduce its duration, regardless of its aetiology.