MIT method was applied to assay the cytotoxicity of three reversors, verapamil (VER), dipyridamole (DPM) and cyelosporin (CSA) in K562, K562/ADM and KB cell lines. S-P immunocytochemical technique was applied to detect expressions of oneoproteins or tumor suppressor oncoproteins in these tumor cell lines before or after treatment with these reversors. Results showed that three reversors were capable of inhibiting to a certair, extent growth of K562 or KB cell lines and reversing greatly adriamyein (ADM)-resistanee in K562/ADM cell line. DPM and CsA were observed to inhibit, partly or wholly, expressions of p53, p16, hci-2, p21 or cerbB-2 oncoproteius. VER showed whole inhibition of expressions of p53, p16, p21 and bel-2 and partly expression of p53 oneoprotein in K562 cell line. These results suggest that growth inhibition in K562 or KB cell Hues by the reversors may be associated with partial or whole inhibition of expressions of p53, p16, p2l or cerbB- 2 oueoproteins. Inhibitions of expressions p53, p16, p21 oncoproteins by VER but not DPM or CsA, may be respossible for reversing activity of VER for ADMresistance in K562/ADM cell line.