The association between haemospermia and hypertension was examined in a case-control study comparing 5 hypertensive patients with haemospermia to 20 age-matched hypertensive men. Patients with haemospermia had much higher blood pressures than hypertensive controls (200/131 mmHg vs 147/90 mmHg; P less than 0.0005/P less than 0.0001), higher left ventricular voltage on ECG (P less than 0.02), and higher concentrations of serum creatinine, proteinuria and renovascular disease (all P = 0.06 vs controls). Haemospermia is associated with severe uncontrolled hypertension. It is not, however, associated with hypertension per se, as the prevalence of hypertension in published series of patients with haemospermia is no higher than that expected in the general population. Men presenting with haemospermia should have their blood pressure measured carefully as they may require antihypertensive treatment urgently.