Clinical studies have reported a positive correlation between the surface roughness of teeth or implants and the rate of supragingival and subgingival plaque maturation. This study compared the surface characteristics of abutments from different implant systems (Astra Tech, Bonefit, Brånemark, Core-Vent, IMZ, and Steri-Oss}. Foreach system, two abutments were examined for surface roughness and surface hardness. The latter served as an indicator for resistance against roughening during professional or habitual oral hygiene procedures. The Ra values (in µm) of the tested abutments were: Steri-Oss, 0.10; IMZ, 0.14; Brånemark, 0.21; Bonefit, 0.23; Astra Tech, 0.27; and Core-Vent, 0.30. The Vickers hardness scores (in VHN) were: Brånemark, 154; IMZ, 208; Astra Tech, 258; Bonefit, 292; Core-Vent, 304; and Steri-Oss, 340. In comparison to most metallographically polished composites, titanium abutments showed a higher initial surface roughness and a slightly higher surface hardness. This may explain, besides the known high surface free energy of titanium, rapid plaque growth on these abutments. Keywords: implants, microbiology, plaque formation, surface characteristics, surface roughness, surface hardness