The results of a prospective study of the development of hypertension and renal stone disease in subjects with increased blood urate are reported and compared with matched controls. None of the 14 patients on Allopurinol developed a renal stone but one untreated control did. For male patients there was a significant difference (p less than 0.01) in diastolic blood pressure between the 2 groups over the 5-year study period, with treated patients having higher blood pressures than untreated controls. This suggests that Allopurinol has had no effect on lowering diastolic blood pressure. Long-term therapy with Allopurinol was effective in reducing mean blood urate levels. It is suggested that blood urate levels are more relevant in predicting renal stone formation and of less value in assessing the therapy and prognosis in hypertension.