By using RT/PCR technique the p53 phenotypes of normal white blood cells (WBC), leukemic cell lines and WBC from myelogenous leukemia patients were performed. The results showed that the p53 mRNA in normal bone marrow WBC was moderately expressed (p53 mRNA/beta-actin mRNA = 0.871 +/- 0.032) while it was not detectable in HL60 and K56z cell lines. The level of p53 mRNA in bone marrow WBC from 21 leukemia patients was significantly down-regulated (p53 mRNA/beta-actin mRNA = 0.433 +/- 0.181, P < 0.01).