The crystal structures of two newβ-adrenergic antagonists, derivatives of propranolol, are reported in this paper. The space groups and unit-cell parameters are: compound1 (C18H24NO4Cl), monoclinic,P21,a=7.215(1),b=8.591(1),c=15.017(1)A,β=95.64(1)°; compound2 (C18H24N2O3), monoclinic,P21/c,a=10.218(3),b=21.616(5),c=8.124(2)A,β=101.28(2)°. The structures were solved with direct methods and refined by full-matrix least-squares techniques toR indices of 0.036 and 0.066, respectively. The molecule of compound1 has an extended external chain, and thus its structure is linear, whereas the molecule of compound2 is compact, and its external chain is twisted in a characteristic way, as is the case of peptides.