The recombinant plasmid PGC was constructed for transcription unit of c-myc gene with diorientation in vitro, to make RNA probes for detection of c-myc mRNA and antisence RNA expression of tranfectant HL^R₆₀-9, which was obtained from HL60 cells transfected with inducible c-myc antisense RNA expression plasmid. The results from HL^R₆₀-9 cells induced by Cd²⁺ indicated that expression of c-myc antisense RNA increased with Cd²⁺ concentration and exposure time, while c-myc mRNA expression progressively reduced. Using immunohistochemical technique no c-myc P62 protein expression was detected. The incorporation of ³H-TdR, ³H-UR and ³HLeu revealed significant suppression of DNA, RNA and protein biosynthesis. It is suggested that the reversion changes previously reported in malignant phenotypes of HL^R₆₀-9 cells and the inhibition of macromolecular biosynthesis mentioned above were associated with the blockade of c-myc gene expression by its antisense RNA.