The aim of this study is to evaluate the influence of various surface treatments on the surface roughness of a lithium disilicate glass ceramic. A total of 25 discs of lithium disilicate glass ceramic were prepared. Specimens were divided into five groups: (1) no treatment, (2) air abrasion, (3) acid etching, (4) Nd:YAG laser irradiation and (5) Er:YAG laser irradiation. Digital images from the surfaces were obtained by means of an atomic force microscope in tapping mode. Surface roughness was measured in 10x10 mu m boxes. Surface roughness data were analysed by one way analysis of variance. The air abrasion group (550 +/- 212 nm) had a significantly higher mean surface roughness value than the other groups. The acid etching group (392 +/- 157 nm) had a significantly higher mean roughness value than the control group (228 +/- 105 nm). Surface roughness of lithium disilicate glass ceramic was not increased by any of the laser irradiation treatments.