Previous studies have shown that the severity of enteric hyperoxaluria can be reduced in hospitalized patients who receive a diet low in oxalate and fat. Little is known of the value of such a diet in the patients' home conditions. Ten patients with hyperoxaluria (greater than 0.45 mmol/24 h) following jejuno-ileal bypass were therefore studied while on their ordinary diet and also on a diet with low-oxalate, low-fat content. The mean urinary excretion of oxalate decreased during the dietary treatment from 1.1 to 0.7 mmol/24 h. The diet was demanding, though not unfeasible for the patients. Careful and regular dietary information, preferably by a dietitian, is recommended in such cases.