ABSTRACTAgitated liquid cultures of basidiomycetes typically produce populations of variably sized, undifferentiated mycelial pellets. We have discovered that cultural or contaminant stress may induce such liquid cultures to form sclerotia in the mycelial pellets. Formation of the multicellular sclerotia was associated with developmentally regulated synthesis of two different types of phenoloxidases, both present in more than one isozymic form. These phenoloxidases are electrophoretically distinct from the phenoloxidases previously reported to be involved in the initial events in the photomorphogenesis of primordia. The“sclerotial”phenoloxidases may be involved in the regulation of three-dimensional multicellular initiation.