Stone analysis has been directed mainly towards establishing and confirming the presence of calcium phosphates, oxalates and a variety of less common constituents such as cystine. Routinely analyses of this sort can be undertaken by the hospital laboratory (10). More sophisticated techniques such as X-ray crystallography have been applied to allow the various forms of phosphate, oxalate and urate to be distinguished e. g. the mono and dihydrates of calcium oxalate (6, 7). The present study using in vivo neutron activation analysis has been aimed at the elucidation of the constitution of urinary tract stones in terms of, not only the major elements, but also the minor and trace element contents.