Two cases of Schwartz-Bartter syndrome are reported. Both were due to malignant anaplasic tumours of the APUD type with multiple abnormal endocrine secretion, and both were accompanied with hypouricaemia of uncertain significance. The authors believe that the association of hypernatraemia with hypouricaemia should alert clinicians to the possibility of a syndrome of inappropriate antidiuretic hormone secretion (SIADH) of malignant origin.