||The use of habitat by eight species of small mammals was investigated by live-trapping and markrecapture techniques in a series of eight grassland plots of different successional age, ranging from 11 months to 10 years at the start of the study, in southern England. Vegetation composition and structure in the grassland plots was investigated by point quadrat and biomass methods. Species richness ranged from 5–6 per plot. The harvest mouse, Micromys minutus, was a relative specialist that dominated the ruderal stage with its abundant annual and perennial forhs, and was absent from the mid-successional stage. The wood mouse, Apodemus sylvaticus, was also a relative specialist, but dominated the opposite end of the successional gradient (the mid-successional stage, with its small trees and shrubs), and occurred infrequently on the ruderal plot. The common shrew, Sorex araneus, pygmy shrew, S. minutus and field vole, Microtus agrestis were relative generalists with no clear habitat preferences. S. araneus was numerically dominant on most plots and was abundant even on the ruderal plot. The midsuccessional stage sustained the greatest total number of small mammals, but the ruderal plot was also well populated. Niche overlap was greatest between the shrews and least between A. sylvaticus and M. minutus. Despite some preferences for mid-successional stages, all species were rapid colonizers of the ruderal plot: first to be captured regularly were M. minutus and A. sylvaticus, followed by the shrews and M. agrestis, all within 1–2 years of establishment of the plot.