Garlic mustard (Alliaria officinalis) is a common weed species associated with woodland borders, hedge rows, and suburban gardens. Garlic mustard plants expressing foliar symptoms of leaf mosaic and vein banding were collected from Franklin and Cuyahoga counties in Ohio. Analysis of symptomatic tissue using viral-associated double-stranded RNA (dsRNA) analysis on 5% polyacrylamide gels and stained with ethidium bromide resulted in the production of a banding profile (four dsRNA bands with molecular weights of 2.6, 2.0, 1.5, and 0.7 × 106 daltons) similar to that of Cucumber mosaic virus (CMV) (1). Symptomatic tissue suspected of being infected with CMV was analyzed with an indirect enzyme-linked immunosorbent assay (iELISA) employing commercially produced antiserum (Agdia Inc.) against the common strain of CMV antiserum confirmed the presence of CMV. Nonsymptomatic tissue reacted negatively to CMV. This is the first report of CMV in garlic mustard in Ohio. Due to the extensive range of this weed and the wide host range of CMV in ornamental and food-plant species, garlic mustard could serve as an alternate host for CMV in many commercially important plant species. Reference: (1) T. J. Morris et al. Plant Mol. Biol. Rep. 1:27–30, 1983.