In this study, adhesion properties of boride layers formed on the surface of AISI 52100, AISI 5140, AISI 440C, AISI 420 and AISI 304 steels were investigated. Boronizing treatment was carried out in Ekabor-II powders at the temperatures of 850 and 950 degrees C for 4h. The properties of boride layers were evaluated by optical microscopy, SEM, X-ray diffraction and micro-Vickers hardness tester. The Daimler-Benz Rockwell-C adhesion test was used to assess the adhesion of boride layers. Test result showed that adhesion of boride layers depended on the dual-phase structure. The stresses at the FeB/Fe2B interphase caused delamination failure and poor interphase adhesion with increase in the depth of hard and brittle FeB-based layer.