The insulin-like growth factors (IGFs) play a pivotal role in brain tumor growth and inhibition of apoptosis. Specific IGF binding proteins (IGFBPs) may enhance or inhibit tumor growth. Moreover, IGFBPs represent tumor markers and their expression correlates with tumor grading and patient survival. Understanding the role IGFs play for the proliferation of brain tumors is a prerequisite for modulating the biology of tumorigenesis. Novel antisense strategies targeting IGF-I or the Type I IGF receptor may offer additional options to patients suffering from malignant gliomas and other CNS malignancies. Clinical trials are currently underway that should demonstrate whether a beneficial effect is achievable in these patients.