The cellulase gene from the alkalophilic Bacillus sp. strain 1139 was cloned in Escherichia coli using pBR322. Plasmid pFK1 was isolated from transformants producing cellulase, and the cloned cellulase gene was found to be in a 4 X 6 kb HindIII fragment. The cellulase gene was subcloned in a functional state on a 2 X 9 kb DNA fragment and its nucleotide sequence was determined. The coding sequence showed an open reading frame encoding 800 amino acids. The pFK1-encoded cellulase had the same enzymic properties as the extracellular cellulase produced by the alkalophilic Bacillus sp. strain 1139, but its Mr was slightly higher.