In an attempt to elucidate the state of acid mucopolysaccharides in nasal polyps, the author investigated histochemically and histopathologically 73 specimens obtained from 64 cases of patients with nasal polyps. The results thus obtained were discussed and summarized as follows ; 1) The surface lining epithelium of nasal polyps contained granule mixtures of a large amount of acid mucopolysaccharides, which was chiefly composed of sulfated mucin, and small amounts of neutral mucopolysaccharides in the distal portion of its cytoplasm. 2) In the infiltrative type of nasal polyp, the surface lining epithelium contained less acid mucopolysaccaride than in the edematous type but more than in the fibrous type. 3) In the stromal connective tissue of nasal polyps, there was an increase in the amount of acid mucopolysaccharide, which was mainly composed of large amounts of sulfated mucin and small amounts of hyaluronic acid. The acid mucopolysaccharide was less in the infiltrative type than in the edematous type but more in the infiltrative type than in the fibrous type. 4) The wall of the small arteries were markedly thickened in the edematous and infiltrative types of nasal polyps but mildly thickened in the fibrous type. In addition, there were depositions of small amounts of acid mucopolysaccharide which was mainly sulfated mucin in the thickened wall of the small arteries. 5) Some of the fibroblasts and primitive mesenchymal cells contained small amounts of granules of acid mucopolysaccharide, which seemed to be sulfated mucin in their cytoplasm. 6) The author thinks that the evidence suggests that the acid mucopolysaccharide observed in the stromal connective tissue of nasal polyps is produced by the fibroblasts, primitive mesenchymal cells, but partially by the endothelial cells.