Buckwheat (Polygonum fagopyrum L.) is an annual medicinal plant useful in convalescence and treatment of anemia. It is widely grown in Europe, where it is sometimes used as human food. In a survey made during 1995 to 1996 in the Emilia-Romagna region (northern Italy), a virus was consistently isolated from plants showing yellow or chlorotic mottle on the leaves. It was mechanically transmitted to herbaceous hosts, including Chenopodium amaranticolor Coste et Reyn., C. murale L., C. quinoa Willd., Gomphrena globosa L., and Vicia faba L. (which showed systemic vein clearing, necrosis of terminal leaves, wilting, and death) and identified by indirect enzyme-linked immunosorbent assay (PAS-ELISA, using A protein) as broad bean wilt fabavirus (BBWV) serotype I. Moreover, elongated, potyvirus-like particles, 750 nm in length, were observed by electron microscopy of leaf dips from symptomatic leaf samples of P. fagopyrum. These particles were identified as turnip mosaic potyvirus (TuMV) on the basis of differential host reactions and by serological assays, including PAS-ELISA, immunoelectron microscopy, and gold-labeled antibody decoration. Both BBWV and TuMV may have been transmitted to P. fagopyrum by the abundant aphid populations from other medicinal plants cultivated in the same location. In particular, Digitalis lanata Ehrh. and Hesperis matronalis L. were found to be infected by the same two viruses (50% of diseased plants). This note represents the first report of BBWV, alone or in mixed infections with TuMV, in P. fagopyrum.