Spores of Glomus macrocarpum Tul. & Tul. were sieved from a calcareous, silty clay loam soil, washed in sterile water, and plated on chit in agar for the isolation of actinomycetes. Of the 190 spores examined, 100 were colonized by one or more chitin-decomposing microorganisms: 82% were colonized by actinomycetes, 17% by bacteria, and 1 % by fungi. Fifty-one actinomycete isolates were classified on the basis of morphological, cultural and biochemical criteria. Tentative identifications to genera and numbers of different isolates are as follows: Streptomyces (29); Nocardia (3); Streptosporangium (1); Streptoverticillium (1); Intrasporangium (1); Nocardiodes (1); and unidentified (15). This is the first study to report the prevalence and diversity of chitin-decomposing actinomycetes associated with spores of a vesicular-arbuscular mycorrhizal fungus in field soil.