To evaluate bone turnover changes occurring during protein-energy malnutrition, serum osteocalcin, a marker of bone formation, has been studied in healthy control, stunted, and severely malnourished (kwashiorkor and marasmus) Senegalese children. Serum osteocalcin levels were dramatically reduced in stunted, kwashiorkor, and marasmic children compared with control children. In addition serum osteocalcin levels of control children living in Senegal were lower (-46%) than those of African children living in France. Interestingly, serum osteocalcin level was not related to its major known regulators (1 alpha,25-dihydroxycholecalciferol, 25-hydroxycholecalciferol, and PTH) nor to stunting, but was related to serum transthyretin and thyroid hormones concentrations. These data suggest that serum osteocalcin level is related to protein-energy status and that bone formation was affected in apparently healthy and in malnourished Senegalese children. Serum osteocalcin could be a potent tool in the study of the alterations of bone formation in malnutrition.