A vegetation survey in Pukaskwa National Park carried out in conjunction with lake, soil, and rock studies resulted in the confirmation of a new shrub species for Ontario. This species. Mountain Bilberry ( Vaccinium membranaceum), is common in the study area. It is found on shallow acid soils in mature and over-mature mixed forests. It occurs in a sparse to moderately dense shrub layer over a usually well-developed herb layer (possibly a response to severe Spruce Budworm defoHation). Lists of vascular plants, bryophytes, and lichens (11 species) associated with Mountain Bilberry are included. Key Words: New species, Vaccinium membranaceum, Mountain Bilberry, Ontario, Pukaskwa National Park.