The upland moorlands of Wales are situated on the oceanic fringe of western Europe, and have experienced a long history of pastoral management. Recent vegetation data are analysed to assess the relative contribution of abiotic and anthropogenic factors to variation in habitat composition among the major upland ranges of this region. From a numerical analysis of plant community cover data, recorded from 65 sites covering 260000 ha, a six-cluster site classification emerged with striking biogeographical coherence. Direct gradient analysis and variance partitioning revealed strong correlation between vegetation composition and spatially-structured climatic gradients, in particular temperature, rainfall and oceanicity; differences in bedrock geology appear to have a lesser role. The analysis also indicates a close correlation between habitat variation and anthropogenic parameters, especially grazing intensity, burning frequency, and sulphur and nitrogen deposition levels. At this regional scale, anthropogenic impacts appear to have accentuated, rather than obscured, vegetation patterns which are primarily determined by climate and other abiotic variables. The findings have considerable relevance for conservation planning and also for predictive studies on the consequences of climatic change for the biota of the uplands of southern Britain.Abbreviations: RDA = Redundancy Analysis.Nomenclature: Gibbons et al. (1993); Rodwell (1991–2000); Tutin et al. (1964–1980).