The cases of 3 sibs presenting with isovaleric acidemia are reported. The first infant died when he was 9 day-old. The two others appear to have benefited from a controlled leucine diet which was introduced from the first days on of life. The clinical symptomatology, highly typical of the disease, is described. Diagnosis was not assessed on amino-acids chromatography but on the chromatography of volatile fatty acids. The mode of treatment is described: peritoneal dialysis, with the object of rounding a crucial cape, and overall controlled leucine diet, but supplemented by essential amino-acids.