Abstract Two kinds of bacteria producing alginate lyase were isolated from ditch sample and they were designated A-1 and A-2 strains. Morphological and physiological properties of the two strains were closely similar to each other, except that the cells of strain A-1 showed flocculation during growth on a medium containing alginate as a carbon source. The cells of strain A-1 produced three kinds of intracellular alginate lyases (A 1-I, A 1-II- 1 and A 1-II- 2). The cells of strain A-2 also contained three kinds of alginate lyases (A 2-I, A 2-II- 1 and A 2-II- 2) in cells. Completely purified A 1-II- 1 and A 2-I enzymes were monomer with a molecular weight of 60,000. A 1-I (partially purified), A 1-II- 1 and A 2-I enzymes were most active at pH 8.0 and hydrolyzed sodium-, potassium- and propylene glycol-alginates at almost the same efficiencies.