Molecular weights, (MW) pH optimum and substrate specificity of multiple forms of phenol oxidases from Kolkhida tea leaves ( Camelia sinensis L.) and microscopic fungus Mycelia sterilia IBR 35219/2 have been studied. It has been shown that Kolkhida tea leaves consist of phenol oxidases with MW 28,000, 41,000, 58,000, 118,000 and 250,000. Duration of M. sterilia IBR 35219/2 cultivation affects formation and activities of multiple forms of phenol oxidases (MW 240,000, 93,000, 58,000 and 41,000) in the culture filtrate. Maximum activity of phenol oxidases is revealed at 36-h duration period of cultivation. By this time Phenol oxidase, mainly, with MW 240,000 is produced. Both Kolkhida tea leaves phenol oxidase with MW 250,000 and M. sterilia IBR 35219/2 phenol oxidase with MW 240,000 are catechol oxidases with similar substrate specificities. Multiple forms of phenol oxidase from tea leaf with MW 118,000±3000 and 58,000±2000 do not reveal hydroxylase activity but they intensively catalyze oxidation of o-diphenols. High molecular weight forms of phenol oxidase of both Kolkhida tea leaves (MW 250,000, 118 00 and 58,000) and M. sterilia IBR 35219/2 (MW 240,000) catalyze the oxidation of catechins, mainly (−)epigallocatecin and (−)epigallocatechin gallate. Theaflavins and thearubugins produced at this time regulate phenol oxidase activity. High concentration of these products completely inhibits activity of phenol oxidase. Phenol oxidases of low molecular weights (MW 28,000 and 41,000) from tea leaves catalyze hydroxylation of monophenols, namely, p-coumaric acid, producing o-diphenols. Phenol oxidase of microscopic fungus M. sterilia IBR 35219/2 with MW 240,000 catalyzes oxidation of green tea extract polyphenols.