In 1995, slug damage and numbers of slugs were estimated in two grass strips and adjacent rape fields. Investigations began as soon as rape seedlings emerged and lasted for five weeks. Slug damage to rape plants 1 m from the grass strips was significantly higher than at greater distances from the strips. Deroceras reticulatum was the most abundant slug species recorded in both grass strips and adjacent rape fields. Arion lusitanicus and Arion fasciatus were much less abundant than D. reticulatum. In one field, D. reticulatum declined steadily with increasing distance from the grass strips and therefore appeared to have caused the majority of severe damage to rape plants close to the strips. This finding was surprising because until now severe slug damage in oilseed rape beside semi-natural habitats has been observed only where A. lusitanicus was abundant.