The aim of this study was to provide a basis for examining the molecular mechanism for the pharmacological action of dopamine HCl (DA) and chlorpromazin HCl (CPZ). Radiationless energy transfer from the surface fluorescent probe, 1-anilinonaphthalene-8-sulfonic acid, to the hydrophobic fluorescent probe, bispyrenylpropane (Py-Py), was used to examine the effects of DA and CPZ on the thickness (D) of the liposomal lipid bilayers prepared with total lipids (SPMVTL) and phospholipids (SPMVPL) extracted from neuronal membranes. The thickness (D) of intact SPMVTL and SPMVPL ($37^{circ}C$, pH 7.4) were $0.914{pm}0.010$ and $0.886{pm}0.009$ (arbitrary units, n = 5), respectively. DA decreased the thickness of both SPMVTL and SPMVPL in a dose-dependent manner with a significant decrease in thickness observed even at $40{ imes}10^{-9}$ M and $40{ imes}10^{-9}$ M, respectively. On the other hand, CPZ increased the thickness of both SPMVTL and SPMVPL in a dose-dependent manner with a significant increase in thickness observed even at $35{ imes}10^{-5}$ M and $35{ imes}10^{-5}$ M, respectively. The sensitivities to the decreasing and increasing effect of the membrane lipid bilayers thickness by DA and CPZ, respectively, differed according to the liposomes in descending order of SPMVPL and SPMVTL. The decreasing and increasing action of DA and CPZ, respectively, on the membrane thickness had many effects that may be responsible for the dopaminergic receptor-DA and -CPZ interaction as well as the protein-lipid interaction.