A female, age 30, suffering from an intractable cystitis, was impossible to cystoscope. Roentgenologic examination showed two shadows in the pelvis. Cystostomy revealed that one of the shadows corresponded to a stone, the other to a hair ball. The latter lay in a diverticulum which represented a paravesical dermoid cyst which had opened into the bladder. The cystovesical, fistulous tract having been dilated and its contents removed, and cyst became practically obliterated.