The growth of four strains of the shiitake mushroom Lentinus edodes in solid substrate fermentation in synthetic oak sawdust logs was studied over a 14-week period. Total extracellular phenol oxidase activity and soluble protein were monitored and biomass estimated as the ergosterol content of the fermented sawdust. It was observed that two of the strains has a similar pattern of phenol oxidase activity with two cycles with maxima at 2 and 8 weeks of mycelial growth prior to fruiting. With the other two strains there was a maximum at week 4. For each strain, phenol oxidase activity increased with the cold shock used to induce fruiting. Phenol oxidase activity was not found to be correlated with either soluble protein or total fungal biomass in the fermented sawdust, which were correlated for each strain. Quantification of biomass from submerged liquid culture on the basis of dry weigh and ergosterol contents showed that the strains fell into the same two groups with respect to the ergosterol to biomass ratio, which was markedly lower than that for a strain of L. lepideus.