3-[(123)I]Iodo-alpha-methyl-L-tyrosine (IMT) is an artificial amino acid which has gained considerable interest in Nuclear Medicine in the last two decades. Although the tracer is not incorporated into proteins it exhibits high uptake in brain tumors and appears to be a valuable tool especially for the diagnostic evaluation and therapy planning of patients with cerebral gliomas. In this paper the present knowledge of the uptake mechanisms and the clinical applications of IMT are reviewed and the clinical perspectives discussed.