In order to investigate whether activities of enzymes involved in nucleic acid metabolism were changed in nasal polyp tissues, enzyme levels of typical nucleases, ribonuclease(RNase) and deoxyribonuclease(DNase) were determined in nasal polyp tissues and were compared with those in normal control tissues. Also measured were concentrations of DNA, RNA and proteins in nasal polyp tissues, and results were as follows : 1) Activities of RNases were significantly higher in nasal polyp tissues than in normal control tissues ; neutral Rnase activity was increased by 92% and acid RNase by 62%. The positive rate of the enzyme activity as a marker for nasal polyp was observed to high(46%) in neutral RNase and low(18%) in acid RNase. 2) While activities of RNase were significantly increased, activities of DNase(neutral, acid and alkaline DNases) remained unchanged, and positive rate of DNase activities as a marker for nasal polyp was also found to be low. 3) Concentrations of DNA, RNA and proteins in nasal polyp tissues were increased by 62%, 46% and 89% respectively, as compared with those in normal control tissues. The positive rates of nucleic acid and protein levels as a marker for nasal polyp were obtained to be high(46% each) in DNA and protein and low(18%) in RNA. 4) Neutral RNases in nasal polyp tissues were isolated in four peaks by DEAE-cellulose column chromatography. The neutral RNases isolated from nasal polyp tissues exhibited the highest activity against polycytidylate(poly C) and virtually on activity was observed against purine polyribonucleotides, polyadenylate(poly A) and polyguanylate(poly G). The RNase activity was observed to be higher with with RNA as substrate than with polyuridylate(poly U). 5) The pattern of nasal polyp tissue proteins separated by polyacrylamide gel electrophoresis appeared to be different from that normal nasal tissue proteins. It was, however, unclear whether proteins specific to nasal polyp was present in the nasal polyp tissues. The results indicated that concentrations of nucleic acids and proteins and RNase activity used as a marker for tissue proliferation and tumor were significantly increased in nasal polyp tissues, but DNase activity known to be involved in development and maintenance of tumors remained unchanged. This may show the one aspect of difference between nasal polyp characterized by tissue proliferation and tumor tissues.