Amyotrophic Lateral Sclerosis is the most common type of motor neuron disease, characterized by progressive degeneration of the upper and lower motor neurons. Sufferers present with symptoms of muscle weakness and this quickly develops on to paralysis and finally death due to respiratory failure within 5 years of disease onset. Although the majority of cases are sporadic, about 10% are familial and it is hoped that through the investigation of these few cases a greater understanding of the disease process, the reasons for its delayed onset and vulnerability of motor neurons will be achieved. Recently a novel mutation linked to ALS was discovered in an evolutionary conserved protein named Vesicle associated membrane protein (VAMP) associated protein B (VAPB). VAPB is an integral type II membrane protein localised at the Endoplasmic Reticulum and thought to have a role in protein transport. The orthologue in Drosophila has been shown to be involved in the homeostatic regulation of bouton formation at the Neuromuscular Junction through an association with the microtubule network. To elucidate the mechanism through which this protein causes ALS, Pennetta et al have created a Drosophila model of the disease by expressing the mutated orthologue in the fly. To complement this model, I have undertaken a number of biochemical experiments to look for potential interactors of the VAP proteins. The yeast two hybrid system utilises the yeast GAL4 transcriptional activator to indicate a protein interaction within a yeast cell and can be used to test a cDNA library for interactors. Through this technique a number of interesting binding partners have been found that may play crucial roles in the progression of the disease.