P-hydroxybiphenyl is used as a dye; an intermediate of resin and rubber. Red light enhancement of biphenyl; green light increasing infectious material is one of the main raw materials of color film and also used as analytical reagent. Colorimetric determination of acetaldehyde and lactic acid, quantitative determination of mural acid. Inhibitors of deoxyribonuclease I. The intermediate of dye, resin and rubber, fungicide, soluizer of water-soluble paint.