SummaryA case of Fanconi’s syndrom is described in an adult male, 56 years old. Physical examination showed deformities of the chest and back suggesting collapsed vertebræ. X rays were confirmative, showing true and pseudofractures in the pelvis and the hips. Clinical examination suggested nervous involvement with bilateral pyramidal signs.Laboratory studies of the blood showed : serum phosphorus±1,0 mgr%, serum calcium 9,2 mgr %, sugar and alcaline reserve are normal. Glucose tolerance test is normal despite the presence of sugar in the urine (8 to 10 gr/a day). Large amounts of P (0,5 gr/a day) are excreted despite the low level of blood phosphorus. Aminonitrogen in blood is normal (5,0 mgr %). Urinary excretion is high (0,55 gr/a day) when the patient is fasting. Paper chromatography of the urine showed an increased excretion of aminoacids when compared to that of normal people.Kidney function studies have shown, with normal filtration rate a decreased capacity to reabsorb glucose and phosphorus. The maximal capacity to reabsorb glucose was 181 mgr with a filtration rate at 100 cc/min. The maximal capacity to reabsorb phosphorus, when-the blood level was increased to 10 mgr%, was 1,5 mgr/min, a very low value when compared to normal values of 4,6 (±1,2) mgr/min. 86%of the filtred phosphorus appeared in the urine at plasma levels around 10 mgr %. At plasma levels as low ns 1,0 mgr %, 16 % were still excreted.Staticin caronamid did not change the renal excretion of phosphorus in this case, a fact that seems confirmative of the view that phosphorus in Fanconi’s syndrom is not excreted by tubular secretion.Administration of large amounts of tricalcic phosphate and of monosodic phosphate brought improvement to the patient. 6 months later osteomalacia was largely controlled. Neurological signs had disappeared. Serum phosphorus and calcium were only little changed, but alcaline phosphatases were increased from 5,8 C. R. to 12,1 U. R.The clinical state was much improved. The patient was able to move arms and legs, to sit on the edge of his bed without help. After five years confinement in bed or chair, walking seems a near possibility.