Thalidomide was withdrawn from the market in the early sixties because of its 
teratogenic effects. Despite forty years of research, the mechanism of 
thalidomide embryopathy has remained unsolved. Thalidomide has various 
immunomodulatory effects. Thalidomide inhibits TNF alpha production, has T-cell 
costimulatory properties and modulates the expression of cell surface molecules 
on leukocytes in vivo. Thalidomide also has anti-angiogenic activity in vivo. 
Angiogenesis plays an important role in the pathogenesis of both solid tumours 
and hematologic malignancies such as multiple myeloma and lymphoma. In clinical 
studies, thalidomide has been used as an inhibitor of angiogenesis. Erythema 
nodosum leprosum is the only registered indication for the use of thalidomide in 
the United States of America. Thalidomide is also effective in the treatment of 
chronic graft-versus-host disease, mucocutaneous lesions in Behçet's syndrome 
and HIV infections, and multiple myeloma.