Protoplasts from Trichoderma koningii were fractioned at varing digestion periods. There were distinct differences between the fractionated protoplasts in CMCase activity and protein content ; namely, protein contents and CMCase activities in the early-protoplasts were higher than the late-produced protoplasts. Reversion frequencies of the early-produced protoplasts. Reversion frequencies of the early-produced protoplasts (0-1hr.) and the late-produced protoplasts (1-2.5 hr.)were 1.25% and 0.56%, respectively. From these results it was assumed that the early-produced protoplasts were more active in physiological metabolism. Meanwhile, in osmotically stabilized liquid medium two distinct reversion patterns of these protoplasts were found. In the first, normal germ tube was developed from the opposite side of the protoplast after the production of an aberrent tube. In the second, reversion occurred through germination of protoplast, but this patterns was uncommon. It is suggested that the the physiological and morphological heterogeneities in protoplast reversion are related to the heterogeneous origins of protoplasts from highly differentiated mycelium.