The free living nematode worm Caenorhabditis elegans (C. elegans ) has been extensively studied by biological, agricultural, and medical scientists for over 40 years. The animal has several characteristics that make it useful as a model organism. For example, the nematodes are transparent, which allows study of embryonic development and gene expression in living animals under the microscope. They also have a very short life cycle of about 3 days and a relatively short lifespan of about 3 weeks, which allow genetic dissection of the mechanisms that affect aging and ultimately determine lifespan. In addition, the mechanism of gene silencing by RNA interference has been discovered in C. elegans and has been developed into a potent reverse genetic tool. Because of the strong conservation of molecular genetic pathways between C. elegans and mammals, it represents a powerful addition to the small animal model repertoire. Genetic mechanisms in human disease, such as Alzheimer’s disease, have been elucidated in C. elegans , indicating its potential as a model for human dementia. Here, we will discuss the existing models, and what they have revealed about the genetic pathways and pathogenesis of different forms of dementia. We will also describe how to set up forward and reverse genetic screens in C. elegans , which can be used to identify additional genes and processes involved in dementia.