The European pine shoot moth, Rhyacionia buoliana (Schiff.), was introduced accidentally into Ontario about 1925, and has since spread throughout the southwestern part of the province south of a line from the south shores of Georgian Bay on the west to Brockville on the east (Fig. 1). Damage to the host is done by the larvae, the feeding of which results in the deformation of the branches and main stems, reducing the potential value of the trees as timber and, in heavy infestations, making young trees unsuitable for the Christmas tree trade. Several species of exotic and native pines are attacked; red pine, Pinus resinosa hit,, Scots pine. P. sylvestris L., and Mugho pine, P. mugho Turra, being the most susceptible. Because of the extensive planting of Scots and red pine in southern Ontario, especially during the last 25 years, the increasing numbers of European pine shoot moth in this area present a problem of great importance. Contributing to an understanding of this important pest, this paper presents a detailed review of the parasites obtained in Ontario since 1954, with some notes on earlier surveys.