Objectives: The finishing of the gingival floor and its margins is regarded to be necessary in Class II cavities, so the aim of this research was to evaluate 4 finishing systems for the cervical margins of Class II cavities, with regard to surface roughness and waviness. Methods: Eighty Class II cavities were prepared in 20 intact molars by a single operator, using a diamond-coated bur (granulometry 80 mu m) mounted on a parallelometer, under magnification (5x, Zeiss) in order to reduce variability. In every tooth, 4 different finishing methods were randomly applied: A: carbide bur; B: straight hand chisel; C: diamond-coated bur 60 mu m; and D: diamond-coated sonic instrument. After that, the gingival floor of each cavity was analysed with an optical profilometer. Mean surface roughness (Ra) and mean surface waviness (Wa) were evaluated with an optical device. Results were analysed with ANOVA after ln-transformation of data. One- and two-way ANOVA was applied. Results: There was no statistically significant difference between the 4 test groups for Ra which was in the range between 0.76 and 0.92 mu m. For Wa, the diamond bur produced significantly lower waviness values (mean Wa 5.2 mu m) than the other three instruments (mean Wa between 5.7 and 7.7 mu m). The variability of Ra and especially Wa was very high: the coefficient of variation of Ra was between 23% and 38%, that of Wa between 52 and 57%. Conclusions: As there was no difference between the four instruments considering surface morphology, the efficient and safe sonic instruments should be chosen over the other three instruments for finishing proximal boxes of Class II cavities.