The primary objective of this study was to discover one or more clusters of compounds which are not equitoxic but display cytoselectivity toward different malignant cells. Furthermore a most important consideration is that such molecules should also display greater cytotoxic potencies to tumors than normal tissues. Two series of compounds are described which meet these criteria, namely the 1-aryl-2-dimethylaminomethyl-2-propen-1-one hydrochlorides 1a-e and 1-aryl-3-dimethylamino-2-hydroxymethyl-1-propanone hydrochlorides 2a-e. A number of these compounds possess marked cytotoxic potencies (IC(50) and CC(50) values within the 10(-6) and 10(-7) molar range) which are greater than these of the reference drug melphalan. Statistical analyses demonstrated that cytotoxic potencies are influenced by the size of the aryl substituents in series 1 and to some extent by the electronic properties of the aryl groups in series 2. The mode of action of a representative compound 1e in HL-60 cells included inducing apoptosis and activation of caspases -3, -8, and -9.