The paper presents the results of laser surface modification of the borided layers produced on the 41Cr4 medium carbon steel (0.43%C, 1.02%Cr). The laser heat treatment (LHT) has been carried out by CO2 laser beam. The microstructure and microhardness have been studied after laser hardening of borided layers. In the microstructure after laser surface modification three zones have been observed: melted zone (eutectic mixture of borides and martensite), heat affected zone (manensite) and the substrate (ferrite and pearlite). The influence of laser heat treatment parameters (scanning rate and power) on the size and microhardness of borided layers has been determined. The layer after boriding and LHT has a lower microhardness than the only borided layer, reducing the hardness gradient between the diffusion layer and the substrate. Probably, the brittleness of this layer is lower. (C) 2002 Elsevier Science B.V. All rights reserved.