The synthesis of a series of (3-hydroxyprop-1-enyl)-substituted 1-(aryloxy)-3-(alkylamino)propan-2-ols is described. These compounds were investigated for their beta-adrenoreceptor blocking properties and their selective of action. Among the o-(hydroxypropenyl)-substituted derivatives we have found some potent noncardioselective beta-adrenoreceptor blocking agents which have a greater blocking action on the beta 2 receptor, thus resembling propranolol. The p-(hydroxypropenyl)-substituted analogues were generally less potent and tended to be cardioselective. The structure-activity relationships are discussed in the light of the hypothesis that the cardioselective of p-amido-substituted (aryloxy)propanolamines is attributable, in part, to binding of the amide group to some additional site on the beta receptor; our findings argue against a similar interaction for the allylic hydroxyl group.