Twenty-eight isolates of R. solani representing anastomosis groups (AG) 1, 2, 4 and 5 were obtained from cankered carrots and hymenia formed on carrot petioles in Minnesota [USA]. Isolates differed in the type and amount of disease they caused and in host specificity on carrots, radishes and potatoes. One AG1 isolate and 6 AG4 isolates caused damping-off of carrot seedlings, slight damage to mature carrot roots and lesions on radish roots. The AG2 isolates were divided into 2 groups based on anastomosis tests and pathogenicity on carrot and radish. Fourteen AG2 type 2 isolates caused damping-off of carrot seedlings and cankers on mature carrot roots, and 2 representatives of this group caused lesions on radish roots. A 2nd group of 3 AG2 type 1 isolates, obtained from hymenia on petioles of carrots, was nonpathogenic on seedling or mature carrots, but caused lesions on radish roots. The AG5 isolates were nonpathogenic on carrot seedlings, roots or radish roots.