The presence of cold sensitivity was investigated in three groups of patients; untreated hypertensives and hypertensives treated by a beta-adrenoceptor blocker (propranolol) or by a combined alpha-and beta-adrenoceptor blocker (labetalol) at two ambient temperatures. At a comfortable ambient (24°C) one-third of the untreated and those treated with beta-blockade only showed cold sensitivity as compared with 16% of patients on the combined therapy. Under conditions of mild cold stress (20°C) cold sensitivity increased in frequency in all three groups, more than half of the untreated and beta-blocked patients were affected and greater than one-third of those with alpha- and beta-blockade. These findings indicate that in the general population of hypertensives treatment with beta-adrenoceptor blockade alone may have little effect on the peripheral vasculature and that a useful degree of protection may be provided by therapy which blocks both receptors.