Viral RNA electrophoresis technique was used to detect rota-virus in 226 children under 2 years of age with acute diarrhea, admitted to the Roberto del Rio Hospital in Santiago, Chile, during the period of June 1979 through May 1980. A group of 50 children included in the aforementioned sample, admitted in win-ter, was compared with a control group of 25 infants without digestive pathology. In these groups, rotavirus was detected in 20 out of 50 children with diarrhea (40%) but not in the controls (0%). A positive diagnosis of rotavirus was found in 66 out of the total of 226 patients (29.2%); its monthly distribution ranged between a maximum of 83.3% (June) and a minimum of 11.1% (October). Speculation: The viral RNA electrophoresis technique for rotavirus diagnosis offers the advantage of simplicity and low cost, being specific and fairly sensitive. It can be very useful in the study of diarrheas, especially in developing countries. This technique can be implemented in any hospital l