Background:The validity self‐reported height (Ht) and weight (Wt) in adolescence has often been reported, but rarely validated. Its reproducibility is unknown.Objectives:To determine the precision and validity of self‐reported Ht and Wt in adolescents from 11 to 14 y of age.Methods:Nutritional questionnaires, including self‐reported Ht and Wt, were performed in low‐income urban Guatemalan schools at 2‐wk intervals in 100 subjects each, in 4 age‐groups (11,12,13,14 y), equally divided by sexes (F,M). Direct Ht and Wt measurements were made after the 2nd interview. BMIs were derived as kg/m2. Similarities in group‐medians and strength of individual associations were calculated.Results:Not all participants self‐reported a Ht and a Wt value on both or either occasion; 30% reported both values both times. For 118 subjects reporting the Ht twice, Spearman correlation was r=0.90 and the medians differed by 2.5 cm F and 0.5 cm M. For Wt repetition in the same subjects, r=0.93 and the medians differed by 1.1 lbs F and 0.0 lbs M. With respect to true BMI and the derived value from self‐reported on the same day, r=0.65.Conclusion:Self‐reported anthropometry may provide valuable estimates at the group level, but is not adequate for individual assessment in this age group.