An N-hydroxyformamidine compound of the following formula or a pharmaceutically acceptable salt thereof: ##STR00001## wherein R.sup.1, A and R are as defined herein. The compounds inhibit 20-HETE-producing enzymes, 20-HETE being involved in the effects of causing microvascular constriction or dilation in major organs (e.g., kidneys, cerebral blood vessels) or of inducing cell proliferation.