The hematocrit (Ht), as an indicator of anemia in individuals and populations, shows variations in relation to mesologic and genetic factors. Anemia is an endemic disease with insufficiently known prevalence in Argentina, in different age and risk groups and particularly in schoolchildren. The aim of this work was to study the variation of schoolchildren Ht in San Salvador of Jujuy city located at 1,200 m.a.s.l. in order to evaluate the prevalence of anemia and to relate these variations to the socio-economic characteristics of the population. The Ht data proceed from 17,580 schoolchildren of private and public schools. They were grouped by age, sex and socio-economic level. Were considered as anemic the children whose Ht was found: a) under a minimal value accepted for the 1200 m level; b) below 2 standard deviations. For the statistical analysis, ANOVA, chi 2 and correlation coefficient were employed. Independently of age, sex and socio-economic level, the average Ht values agree with those adjusted for the altitude. We observed: a) statistically significant intersex differences, males showing higher values than females; b) a trend to the Ht augmentation in relationship to the increase of the socio-economic level. Independently of the criterion used the prevalence of anemia was low in both sexes, age groups and in all socio-economic levels. Ht values: a) are representative of a schoolchildren population located at a moderate altitude; b) in spite of a trend to decrease in the low socio-economic level, this did not surpass, in most cases, the critical anemia level; c) are not indicative of malnutrition in the schoolchildren examined.