Structure-activity studies were carried out on a series of antihypertensive 1-(2-aminoethyl)-3-(substituted phenyl)thioureas. From this class of compounds, the 2,6-dichlorophenyl analogue 2 was found to have potent oral antihypertensive activity in two hypertensive rat models and the renal hypertensive dog. In addition to its effect on blood pressure, 2 displayed sedative effects which had a marked species specificity.