Mild hypercalciuria has been observed in hypertension, but it is not yet established whether the prevalence of urinary stone disease is increased as well. Data from the cross-sectional phase of the Gubbio Study--a population-based survey on hypertension involving 5376 subjects (84% response rate)--have been analysed to address this issue, defining as hypertensive those subjects with diastolic pressure falling within the fifth quintile for each sex- and age-specific category, and/or under regular antihypertensive treatment. The prevalence of a positive history for urinary stone (radiographic and/or surgical evidence, and/or stone excretion) was increased by over 50% (P less than 0.01) in treated and untreated hypertensives. None of the 136 subjects with a positive urinary stone history were hypercalcaemic and none had renal failure.