A premature baby had severe hypertension associated with idiopathic arterial calcification of infancy. Despite the fact that there was laboratory evidence of renin-mediated hypertension, the disease was refractory to specific renin antagonist and failed to respond to conventional medical treatment. Prostaglandin E1 (PGE1) infusion (dosage range 0.017-0.068 microgram/kg/min) promptly controlled hypertension on two occasions. The drug was given for a total of 65 days and then stopped after the appearance of severe thrombocytopenia; other side effects included sporadic hyperthermia and irritability. Blood pressure was then stabilized satisfactory by a multiple-antihypertensive regimen. In the light of these findings, we believe that PGE1 infusion is a possible therapeutic alternative for babies with idiopathic arterial calcification complicated by severe hypertension refractory to conventional treatment.