2-(2-Phenoxyphenylimino) imidazolidine and related compounds (IV and XII) were synthesized and evaluated for hypotensive activity in rats. Most of the 2-aryliminoimidazolidines (IV) were synthesized via the aniline derivatives (VI) by two different methods. Some imidazolidines (IV) were found to be significantly active, with 2-(5-chloro-2-phenoxyphenylimino) imidazolidine (IV-19) being more active than prazosin, the reference compound. The mechanism of action of IV-9 may involve the blockade of peripheral α-adrenergic receptors. This paper describes the synthesis, pharmacology, and structure-activity relationships of the 2-(2-phenoxyphenylimino) imidazolidines.