The effects of coniferous afforestation on rove beetles (Coleoptera, Staphylinidae) was investigated in Kielder Forest in 1988 by pitfall and turf sampling in plantations of various age and in unplanted sites. Tree planting decreased habitat availability for most beetles, but provided new habitat for forest species. The greatest abundance, species richness and diversity occurred in non-afforested sites. Site ordination demonstrated an upland group on acid soils and a lowland group on mineral soils, with wet and dry components; species ordination was similar. A central forest group was due to both forest species and original species being maintained. Similarly, classification separated closed-canopy forest sites with little ground vegetation from the remainder. Afforestation had increased habitat diversity by adding trees, rides and roads to the original habitats, but diversity per unit area had decreased Forest managers should aim to increase staphylinid diversity 'by design', particularly by varying tree species and age class so as to develop greater biological and structural diversity. Habitat diversity could further be enhanced by conserving representative areas of former land use, such as farm fields, river banks and open moorland; active management might be necessary to sustain these. Staphylinid species are favoured by forest edge habitats, so would gain from the integration of small habitat units within plantations, resulting in a beneficial 'knock-on' effect by being food for birds and small mammals.