Abstract: Studies on the occurrence of pathogenic root-infecting fungi in different crop sequences in South Finland revealed Microdochium bolleyi (Sprague) de Hoog & Hermanides Nijhof on roots and stem bases of barley and wheat. The fungus was usually isolated together with the major pathogens Gaeumannomyces graminis (Sacc.) v. Arx. & Oliver, Bipolaris sorokiniana (Sacc.) Shoem. and Fusarium species. The cultural and morphological characteristics of the isolates examined agreed well with the original description of M. bolleyi. The fungus was most prevalent on mature cereal roots. Roots of barley and wheat were more often inhabited by M. bolleyi than those of oats or non-graminaceous plants. In crop sequences barley increased, but oats decreased the number of roots invaded by M. bolleyi.