Reports of Melon et al.  and Hodgkinson  regarding the efficacy of succinic acid or its derivative (salt) in reducing the endogenous synthesis of oxalate are conflicting. The possible application of succinic acid as a potential inhibitor of oxalate synthesis, and the biochemical alterations resulting therein, has been studied in 10 idiopathic stone-forming patients (6 primary stone-formers and 4 recurrent stone-formers) and in 21 normal adult rats. In rats no significant changes in oxalate excretion were observed during the 4 weeks of succinic acid administration (500 mg/100 g BW/day) and 2 weeks therafter. In the clinical trial of 3 months, where stone-formers were given 20 g/day of succinic acid, the post-therapy values of urinary oxalate excretion showed a singificant drop ( less than 0.001) as compared with those of pretherapy--recurrent stone-formers showing a more marked decrease (63%) than primary stone-formers (49%).