The fruit extracts of ripening cv. Harumanis mango contained a number of glycosidases and glycanases. Among the glycosidases, β-d-galactosidase (EC 3.2.1.23) appeared to be the most significant. The enzyme activity increased in parallel with increase in tissue softness during ripening. Mango β-galactosidase was fractionated into three isoforms, viz. β-galactosidase I, II and III by a combination of chromatographic procedures on DEAE-Sepharose CL-6B, CM-Sepharose and Sephacryl S-200 columns. Apparent K m values for the respective β-galactosidase isoforms forp -nitrophenyl β-d-galactoside were 3.7, 3.3 and 2.7 mM, and their V m a x values were 209, 1024 and 62 nkat mg - 1 protein. Optimum activity occurred at ca pH 3.2 for β-galactosidase I and II, and pH 3.6 for β-galactosidase III. Mango β-galactosidase and its isoforms have galactanase activity, and the activity of the latter in the crude extracts generally increased during ripening. The close correlation between changes in β-galactosidase activity, tissue softness, and increased pectin solubility and degradation suggests that β-galactosidase might play an important role in cell wall pectin modification and softening of mango fruit during ripening.