The authors investigated the possibility of using PCR to dsetect the deletion of gene or loss of heterozygosity (LOH) of gene in biopsies. With some aids, such as selection of PCR cycle number, choice of internal control and screening of samples, the authors detected the deletion of GSH Clone 7 in nasophryngeal carcinoma (NPC) by PCR-Southern, and successfully found one case which partially deleted GSH Clone 7. This results was confirmed by image densitometry. Through this study, an available method to detect the deletion of gene by PCR is provided.