The growth of protein-energy malnutrition (PEM) in children with prevalence of endogenous factors of the causes of development has not been decreasing in the Russian Federation and all over the world for the last decades. This determines the relevance of multifaceted study of this pathology. Consequences of PEM suffered in early childhood can have a remote character of realization and influence on human health during the whole life. A separate problem of PEM is the identification of mild forms of pathology, which are often missed. The pathogenesis of PEM is insufficiently studied, in particular, the variability of pathology development depending on gender. The aim of the research was to characterize the peculiarities of the blood metabolic profile of infants at the initial stage of PEM with regard to gender. Material and methods. 38 children (20 boys, 18 girls) aged from 1 to 12 months with the degree I of PEM were examined; the comparison group consisted of 30 children (18 boys, 12 girls) aged from 2 to 12 months. Laboratory monitoring included general and biochemical blood tests with evaluation of such parameters as the content of total protein, albumin, hemoglobin, transferrin, urea, creatinine, glucose, lactate, pyruvate, triglycerides, the activity of lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, creatine phosphokinase, using hematological analyzer (MEDONIC, Boule Diagnostics AB, Japan) and biochemical analyzer (Cobas Integra 400plus, Roche Diagnostics, Switzerland). Results. In children with a mild degree of PEM the blood levels of total protein, albumin, hemoglobin, transferrin didn't differ from that in the comparison group. Against this background, there is an increase in blood serum urea level in all children and a significant increase in creatinine level, which is most pronounced in girls, in whom this indicator is 2.5 fold higher than in the comparison group and by 79% higher than in boys (p≤0.05). In combination with body weight deficiency, this characterizes the development of catabolic stress. A decrease in blood glucose level was detected in all children of the main group; a decrease in triglycerides was revealed in boys (-33%; p≤0.05) with stability of the index in girls. The increase in pyruvate blood serum level in boys (+21%; p≤0.05) with a tendency to decrease in girls is accompanied by a significant elevation in the lactate/pyruvate ratio (by 75% in boys and 3 fold in girls, p≤0.05). Conclusion. There are gender peculiarities of metabolic in children of the first year of life with a mild degree of PEM. In male children there is a decrease in the levels of glucose and triglycerides as energy substrates with the orientation to the ketosis formation. In girls, a more intense character of catabolic stress is observed with stable blood levels of triglycerides with a tendency to develop lactacidosis.