The objective was to determine the level of effectiveness of the educational program about the prevention of acute diarrhea to improve knowledge and practices in mothers of Clas Pillcomarca, January to May 2011. This is a quantitative study, and according to the data analysis is quasiexperimental of one group with one pretest and two posttests. The sample was 25 mothers. We used a questionnaire that applied sociodemographic characteristics of mothers and measured the cognitive level about acute diarrhea: definition, risk factors and preventive measures, before and after the program; also an observation guide was applied to evaluate the preventive measures that mothers use before and after the educational program. In order to evaluate the effectiveness of this program the statistical test of ranges with Wilcoxon sigh was applied. About the cognitive level we had as a result a statistical ...