One hundred and sixteen (3.5%) of 3,300 specimens submitted by 72 patients as urinary stones were artifacts, i.e. not formed of accepted constituents of urinary calculi. The laboratory diagnostic methods included infrared and wet chemical analysis, and X-ray diffraction. Twenty-eight were of organic origin and some of these were undoubtedly submitted by accident as calculi. Eighty-eight were of mineral origin, mainly quartz and feldspar, and it is believed that the great majority were submitted for secondary gain or for psychiatric reasons. Ten patients each submitted from 2 to 10 artifacts. Five cases studies are presented which illustrate some confounding clinical and laboratory findings. Spurious stones can lead to difficult clinical and laboratory problems.