Although cover crops contribute many benefits to organic and conventional agricultural systems, they may play a significant role in the epidemiology of soil-borne diseases. A 2-year study shows that Sclerotinia minor, which causes lettuce drop disease, is a pathogen of phacelia, lana woollypod vetch and Austrian winter pea cover crops. Greenhouse and field inoculations failed to result in S. minor infections of oilseed radish, barley and fava bean cover crops. It appears these three cover crops can be safely incorporated into lettuce rotations without increasing the occurrence of lettuce drop.