This study began as an investigation of reported urinary tract disorders among uranium workers in eastern Tennessee. The facility processed depleted and natural uranium (7440611) and thorium (7440291) from 1957 through 1970, and enriched uranium after 1970. The target population included highly exposed active, retired and disabled production workers with 20 years employment before 1986; a low exposure group of senior office and laboratory workers; minimally exposed guards, aged 40 to 65, exposed recently at the facility; and unexposed dairy workers from a nearby town. The principal result was an increased risk of stones among males in eastern Tennessee. At highest risk were persons with a positive family history whose urine was supersaturated with calcium-oxalate. Biochemical factors influencing the risk of lithogenesis were hypercalciuria, hyperoxaluria, and low urine volume. The occurrence of stones among uranium workers bore no relation to the intensity or duration of occupational exposure. Stones were slightly less common in workers with direct exposure to uranium and thorium than in unexposed workers. Stone occurrence was similar in the uranium and dairy workers. The authors conclude that the risk of stones was regional rather than occupational.