The precise relationship between urine composition and stone formation has not yet been completely understood. The object of this work is to study some constituents of the urine in stone formers and normal subjects in a trial to correlate stone formation with urine composition. Urinary levels of oxalic acid, uric acid and phosphate were elevated in oxalate, urate and phosphate stone formers, respectively, while in the urine of mixed stone formers both oxalic and uric acids were increased. Urinary levels of ascorbic acid, citric acid and mucopolysaccharides in all groups of patients were significantly higher than the corresponding control levels. Although oxalic acid, uric acid and phosphate concentrations were high in their respective stones, the concentrations of these constituents were nearly the same in the mixed stones. Also Ca2+ concentration was higher in stones of oxalate and mixed stone formers than in stones of urate and phosphate formers. Exceptionally, magnesium was high in stones of phosphate stone formers. It is recommended that urinary contents of oxalate, urate and phosphate have to be minimized to overcome stone recurrence.