In this review we discuss the activity of an ecologically significant group of psychrophilic bacteria, which are involved in the hydrolysis of plant cell wall polymers. Until now these organisms have been largely overlooked, despite the key role they play in releasing organic carbon fixed by primary producers in permanently cold environments such as Antarctica. This review details a specific group of plant cell wall polymer-degrading enzymes known as beta-glycanases. Studies on "cold" enzymes in general are in their infancy, but it has been shown that many exhibit structural and functional modifications that enable them to function at low temperature. beta-Glycanases in particular are intriguing because their substrates (cellulose and xylan) are very refractile, which may indicate that their "cold" modifications are pronounced. In addition, mesophilic beta-glycanases have been extensively studied and the current state of our knowledge is reviewed. This body of information can be exploited to enable meaningful comparative studies between mesophilic and psychrophilic beta-glycanases. The aim of such investigations is to obtain a deeper insight into those structural and functional modifications that enable these enzymes to function at low temperature and to examine the evolutionary relationship between mesophilic and psychrophilic beta-glycanases.