57Fe backscattering Mossbauer phase analysis of the ASTM A295-70 type chromium bearing steel gas was performed for samples with varying phase composition achieved by gas carburization up to 3 wt% C followed by standard hardening, i.e. austenitizing and quenching procedures. Variations of contents of principal metallographic phases (alloyed martensite, austenite, magnetic and non-magnetic carbides) were determined and compared with reported X-ray data. Results are discussed in connection with the composition and heat treatment. Good mutual agreement of results was found, the Mossbauer phase analysis being superior for distinguishing magnetic and non-magnetic carbides, for finding the dependence on composition and also for detecting alloying element segregation. On the other hand, the Mossbauer method of determination of a small content of alloyed retained austenite suffers from the small difference between its satellites and non-magnetic carbides.