Severity of hypertension may be defined in terms of the height of the arterial pressure, or the degree of organ damage present or the resistance to drug therapy. These definitions do not necessarily overlap in the individual case. A variety of drugs is now available for treatment of the severe case however defined, but results of current treatment of such cases in practice have not reduced the risk of stroke or of myocardial infarction to that of the age-and sex-matched normotensive population. Data from which to select drugs with favourable effects on left ventricular hypertrophy, glomerular hyperfiltration or the cerebral circulation are scanty and need amplification. Choice of drug therapy in current circumstances remains empirical, although there are probable advantages in the use of converting enzyme inhibitors or calcium antagonists in the treatment of severe hypertension.