Abstract. Improved eddy current techniques and a method of magnetic hysteresis measurement were applied for nondestructive inspection of thickness of the hardened surface layer of the steel injectors of diesel engines. A monotonic correlation was found with enough sensitivity and acceptable signal/noise ratio between the electromagnetic parameters and the thickness of the layer. Both the hysteresis and the eddy current methods show very similar types of the correlation. Based on these results, practical application of these novel methods can be realized instead of the presently used destructive tests for inspection of the steel injectors of diesel engines.