Carbapenems are the drugs of choice in the treatment of serious infections caused by multiresistant Gram-negative bacteria. Clinically and epidemiologically, resistance to these beta-lactams poses the highest risk. In enterobacteria, two common mechanisms can cause the resistance to carbapenems: (1) hydrolysis of carbapenems by beta-lactamases and (2) outer membrane impermeability. The focus is on types of carbapenemases described so far, detection methods, epidemiology of and therapeutic options for infections caused by carbapenemase-producing enterobacteria. Attention is also paid to the mechanisms involved in the control of outer membrane permeability, i.e., reduced porin expression or changes in the porin structure that prevent carbapenems from entering the Gram-negative bacterial periplasmic space.