Using X-ray analysis and electron microscopy, we have studied the behavior of carbide particles in maraging steel with enhanced carbon content. It is shown that carbide particles are present in steel after almost all heat treatments owing to their formation in the austenite during heating before quenching or very rapid new nucleation during tempering. This differentiates the investigated steel unfavorably from known heat-resistant and creep-resistant Cr-Ni-Mo austenitic and improved steels.