ABSTRACT
	The relations between the microstructure characteristics and the resistance of carbon-manganese steels to hydrogen induced cracking (HIC) were studied for plates used in oil and refinery industry. Steels differed in the non-metallic inclusion characteristics and in the microstructure (heat treatment). Testing of HIC resistance was performed in accordance with NACE TM 0284 standard. As to heat treatment, the beneficial role of quenching and tempering was confirmed but also that of "high" temperature normalising performed at 1000°C. For those steels, microstructure of which consisted predominantly of ferrite and pearlite, the susceptibility to HIC increased with the degree of the local enrichment of pearlitic bands especially in manganese and with the growing degree of banding. The role of manganese sulphides was less pronounced.