OBJECTIVE: To evaluate body composition changes using bioelectrical impedance analysis and skinfold thickness measurements in infants from tropical areas who become stunted between 4-18 months of age. DESIGN AND MEASUREMENTS: Follow-up study. Extracellular water to total body water ratio index (length(2)/resistance at low to high frequency), peripheral fat (tricipital and subscapular skinfold thickness), and length-for-age index were studied at 4 and 18 months of age. SETTINGS: Low-income areas in four tropical regions (Congo, Senegal, Bolivia and New Caledonia). SUBJECTS: Infants were included in the analysis provided they were neither stunted nor wasted at 4 months. Two groups of infants were compared, those that were stunted at 18 months (n=61) or not (n=170). RESULTS: The extracellular water to total body water ratio index and the sum of skinfold thickness measurements were similar in the two groups at 4 months, and only the extracellular water to total body water ratio index was significantly different at 18 months. When no stunting appeared between 4 and 18 months, the change in the extracellular water to total body water ratio index was not linked with variations in length-for-age, and presented the expected pattern of variation in body water compartments. When stunting occurred, variation in length-for-age was related to significant changes in the extracellular water to total body water ratio index, the biggest increase in the proportion of extracellular water being found in the most stunted infants. Variations in the sum of the two skinfold thickness measurements presented the expected pattern for the 4-18 months growth and did not differ between the two groups. CONCLUSIONS: Multifrequency resistances suggested that stunting was associated with a lack of the expansion of the intracellular compartment that is expected during normal growth of cell mass, together with preserved fat mass. SPONSORSHIPS: Supported by grant 92L0623 from the French Ministry of Research, and by Institut de Recherche pour le Développement (IRD).