Electron-impact ionization of Ca atoms from metastable states has been investigated using a crossed atomic and electron beam technique. The value of the total ionization cross section from the 4s4p 3 PJ metastable states at an electron energy of 4-20 eV was determined. It has been found that ionization cross sections from the metastable and ground states differ considerably. Such a discrepancy is mainly due to the different mechanisms of ion formation from the metastable and ground states. The obtained results are compared with those calculated using the classic mechanics binary approximation.