The daily urinary excretion of calcium, oxalate, glycosaminoglycans and uric acid, and the 24-h urinary pH and volume were measured in 61 normal men and in 81 men with a history of renal stone disease. The following features of these data were noted: No significant difference could be demonstrated between the stone-formers and normals with respect to any of the variables measured. The values of each of the urinary parameters were positively and significantly correlated with those of at least two other parameters in one or both subject groups. The probability density histograms constructed from the data for each urinary variable in each subject group were unsuitable as the basis for calculation of individual relative risk factors. Thus it was concluded that the data were inappropriate for the calculation of "overall relative probability of forming stones" (P'SF) and that such an index is unlikely to be of use in the assessment and management of stone-formers attending a general hospital out-patient clinic.