The aim of this work was to evaluate the vitamin B12 content and profile of cobalamin bioactive forms in raw and cooked beef. The study showed that vitamin B12 distribution is unequal among beef muscles. The content of this nutrient ranges from 0.7 to 1.5 μg/100 g of tissue. In beef, three biologically active forms of vitamin B12 were determined, i.e.: methylcobalamin, adenosylcobalamin and hydroxycobalamin; the dominating form of vitamin B12 was adenosylcobalamin (68% of total cobalamins). The process of roasting and grilling had little effect on the vitamin B12 content in the final product as compared to the raw meat. The fried product was characterised by about a 32% lower content of cobalamins than in raw meat.