Quantitative structure-activity relationship analysis using theoretical molecular descriptors was done on a set of 30 1,4-benzodioxan (WB-4101) related compounds which are alpha1-adrenoceptor antagonists. The results obtained confirm quantitatively and in terms of reactivity and molecular shape descriptors, the results of previous qualitative structure-activity relationship studies. It was found that the protonated amine function plays a crucial role in the potency of the alpha1-adrenoceptor antagonism due to a charge reinforced hydrogen bond with a primary nucleophilic site of the receptor. Furthermore, the more electrophilic (high SN1LUMO values) the NH2+ group, the stronger the charge reinforced hydrogen bond with the receptor and the higher the blocking activity. It was also found that the three-dimensional shape of the antagonists is more similar to the shape of the most active reference molecule (WB-4101) the more potent antagonists are. Finally, the reactivity (E(LUMO)) and the ad hoc shape (V(D)(norm)) descriptors were used to obtain a bilinear equation which accounts for about 77% of the total variance in the pharmacological data.