Immunotherapeutic approaches for treating Alzheimer's disease were first described in 1999. A clinical trial using an active immunization with Abeta1-42 was initiated shortly thereafter, but it was halted early because of serious safety issues (acute meningoencephalitis in 6% of the treated patients). Despite this drawback, encouraging data from preclinical and clinical data were available, prompting researchers to seek alternative approaches for safer active and passive immunization. Currently, several passive and active immunotherapeutic approaches are being tested in clinical trials. However, our understanding of the mechanisms behind immunization in neurodegenerative disorders is still incomplete. In this review we present the current status of the different approaches in relation to Alzheimer's disease as well as to other neurodegenerative disorders.