We designed and synthesized twelve new 3,4-dimethoxybenzoyl-piperazine derivatives. These chemical structures (TM-1-TM-12) were confirmed by means of IR, MS, H-NMR and elemental analysis. Compounds (OPC-8212 TM-1, TM-2, VPA) were tested for positive inotropic activity. The results showed that compounds OPC-8212 and VPA possessed positive inotropic activity (P < 0.05). Further pharmacological studies will be made.