The chemical environment of Cu(II) adsorbed to the boehmite (AlOOH) surface at pH 6.5 is examined by electron paramagnetic resonance and X-ray absorption spectroscopy. Adsorbed Cu(II) is always coordinated by four oxygens in an axially symmetric ligand field when adsorbed under our experimental conditions. The Cu-O bond distance is approximately 1.94 A. An oriented, inner-sphere Cu(II) surface complex is observed at low surface loading (<0.2 μmol/M2). A second population of Cu(OH)N (H2O)X(2-N)+ outer-sphere complexes is proposed at higher surface loadings to explain X-ray absorption fine structure results. Cu(II) strongly resists any tendency to form a surface precipitate on boehmite at pH 6.5. The presence of specifically adsorbing anions had little effect on the local chemical environment of adsorbed Cu(II). Copyright 1997 Academic Press. Copyright 1997Academic Press