Data are presented from a study of growth from birth up to six years of age of 2,596 children of both sexes from two socio‐economic groups in Bogotá, Colombia, South America. The differences in weight and height of children from both socio‐economic groups were noticeable. The progressive deceleration of growth from the age of six months was very marked in children from low socio‐economic groups. This could perhaps be attributed to the negative influence of improper nutrition following weaning and also to the frequent infection processes which occur at such ages. A comparison was made with American standards. Colombian boys and girls from the upper socio‐economic classes attained a similar growth to North Americans during their first year of life. Thereafter, the growth achievement fell slightly below the American standards. The growth achievement for Colombian boys and girls from low socio‐economic levels fell below the American and Colombian upper socio‐economic groups from birth onwards.