A novel actinomycete, designated strain GUI 15(T), isolated from the root nodules of a Pisum sativum plant was characterized taxonomically by using a polyphasic approach. The 16S rRNA gene sequence of strain GUI 15(T) showed highest similarity to Micromonospora pattaloongensis TJ2-2(T) (98.7 %) and Polymorphospora rubra TT 97-42(T) (98.5 %). Phylogenetic analysis based on the gyrase B gene also supported the close relationship of these three strains, but indicated that strain GUI 15(T) should be assigned to the genus Micromonospora. Chemotaxonomic results confirmed the position of the isolate in the genus Micromonospora, but revealed differences at the species level. The novel strain could be distinguished from recognized Micromonospora species by using a combination of physiological and biochemical tests. Based on these observations, strain GUI 15(T) is considered to represent a novel species of the genus Micromonospora, for which the name Micromonospora pisi sp. nov. is proposed. The type strain is GUI 15(T) (=DSM 45175(T)=LMG 24546(T)).