In the present climate of limited resources and long waiting lists, it is not surprising that there is more emphasis on making sure that psychological treatments are not only clinically sound but also cost-effective. One solution to this is to provide time-limited, focused interventions such as cognitive therapy. Another obvious solution is to deliver treatment in groups rather than individually. However, what evidence is there that therapy can be delivered as effectively in groups as individually? This review will look at which different formats have been tried, what the advantages and disadvantages of those formats might be, which client groups have been targeted for cognitive- behavioural group therapy (CBGT), and whether a group format in general offers any advantages over individual CBT. Outcome studies and their implications for the use of CBGT are considered. Results suggest that, in most client groups, there is little difference in efficacy between group and individual CBT, although there is some evidence that results for some types of patient can be disappointing in CBGT. It may be that the best compromise in terms of cost- effectiveness between quality of therapy and quantity of patients treated is offered by large-scale psychoeducational didactic group therapy.