Resseliella theobaldi (Barnes), which was first described from southeast England in 1920, has become a major pest of commercial raspberry production throughout Europe. It was first reported from Scotland in 1973. The history of its spread in Europe is reviewed and the results are presented of a survey on its distribution in Scotland carried out in August-September 1973, 1974 and 1976. First-year canes of 2 cultivars were examined in 122 plantations. In 1973, the midge was locally distributed in the main raspberry-growing areas of east-central Scotland. By 1976, it was common throughout the main raspberry-growing districts and in Lanarkshire, but larvae were rarely found in northeast Scotland or in the Borders.Larvae were most commonly found in the bottom 20-cm region of first-year canes on which the outer tissues had started to split. The most likely explanation for the upsurge of the pest in Scotland during the period seems to be the introduction of susceptible cultivars and the occurrence of climatic conditions favouring the early splitting of canes.