Validamycin A has been used to control some diseases caused by Rhizoctonia solani, particularly sheath blight of rice plants. Validamycin A is the major component of the validamycin complex produced by Streptomyces hygroscopicus subsp. limoneus, which comprises the ten components: validamycins A ~ G and validoxylamines A, B and G. In the course of purification of pseudo-tetrasaccharides (validamycins C, E and F), a new pseudo-tetrasaccharide, validamycin H, was found. In this communication, we report the isolation, structure elucidation and biological activity against R. solani of the new pseudo-tetrasaccharide, validamycin H.