Novel piperzine derivatives substituted on one nitrogen by an aromatic system and on the other nitrogen by (2,5-dioxopyrrolidin)-1-yl) alkanes or (2,6-dioxopiperidin-1-yl) alkanes have been found to exhibit selective .alpha..sub.1A adrenergic activity. The compounds are useful for treatment of disease conditions, such as peripheral vascular disease, congestive heart failure, hypertension and especially benign prostatic hypertrophy.