A series of para-substituted phenoxypropanolamines has been synthesized and tested for beta-adrenoceptor blocking activity. Some derivatives (8, 11, 12, 20, 21) exhibited greater in vitro potency than the reference drugs metoprolol and propranolol. This series, in contrast to propranolol but similar to metoprolol, possesses cardioselectivity. The 3-[p-[(cycloalkylmethoxy)ethyl]phenoxy]-1-substituted-amino-2-prop anol derivatives 8 (cyclopropylmethoxyethyl: betaxolol) and 11 (cyclobutylmethoxyethyl) produced antihypertensive effects in spontaneously hypertensive rats. Betaxolol (Kerlon, 8) was found to exhibit an appropriate preclinical pharmacological and human pharmacokinetic profile (elevated oral bioavailability and prolonged plasma half-life) for the treatment of chronic cardiovascular diseases such as hypertension and angina.