The resurgence of interest in thalidomide in the last decade has been 
remarkable. Thalidomide has established its own niche market particularly for 
the dermatological manifestations associated with HIV, Behçet's disease, 
graft-versus-host disease and systemic lupus erythematosus. To a large extent 
this has resulted from initial empirical uncontrolled studies in conditions 
resistant to other drug therapies. Appropriate trials are now being published 
for most of the prevalent indications. Thalidomide produces partial inhibition 
of tumour necrosis factor-alpha production in vivo but recent data reveals that 
it can also act as a co-stimulatory molecule for T cell activation in vitro, 
resulting in increased production of interleukin-2 and interferon-gamma. Hence 
in addition to monocyte inhibitory activity, thalidomide can exert a 
co-stimulatory or adjuvant-like effect on T cell responses. The unraveling of 
the molecular basis of thalidomide's therapeutic effects would suggest that an 
expansion of the use of thalidomide and its analogues in other conditions is 
highly likely. It remains imperative, however, that physicians using this 
fascinating drug are familiar with its risks and adverse effects.