P262 endoglucanase and cellobiase genes, cloned on a 4·9 kb DNA fragment in the recombinant plasmid pHZ100, were expressed from their own promoter in . Active carboxymethylcellulase and cellobiase enzymes were produced, but there was no degradation of Avicel. The endoglucanase activities observed in cell extracts of HB101(pHZ100) differed in their pH and temperature optima from those previously reported for P270. Complementation of and mutations by cloned DNA was also observed.