Activities of deoxyribonuclease(DNase), ribonuclease(RNase) and RNase inhibitor were determined in the laryngeal cancer tissue to evaluate the use of nuclease and nuclease inhibitor as biochemical markers for laryngeal cancer. Also the enzymes and enzyme inhibitor in the laryngeal cancer tissue were analysed by a DEAE-cellulose column chromatography to understand the nature of laryngeal cancer. Concentrations of RNA and protein were unchanged but DNA content in the laryngeal cancer tissue was significantly increased. Acid DNase and RNase inhibitor activities were increased, and RNase activity was unchanged in the cancer tissue. The positive rates of DNA content, activities of acid DNase and RNase inhibitor as markers for laryngeal cancer were high, suggesting the use of three parameters as biochemical markers for the cancer. Proteins in the laryngeal cancer tissue were seperated by a DEAE-cellulose column chromatography into 7 peaks, of which a single protein peak was specific to the cancer. Acid DNase was seperated as a single enzyme peak and the enzyme thus purified was highly active toward double stranded DNA. Neutral RNase was seperated into three isozymes(RNase isozymes IV, V and VI), of which RNase isozymes IV and V were acitivated and RNase inhibitor activity associated with these two isozymes were elevated. These results indicated that acid DNase, RNase isozymes IV and V and RNase inhibitors complexed with three isozymes in the laryngeal cancer tissue might play roles in carcinogenesis and suppression of laryngeal cancer.