Amyotrophic Lateral Sclerosis (ALS) is an aggressive, deadly disease. ALS leads to destruction of the neural pathways which control the conscious movements of the muscles. This destruction leads to muscular dystrophy with increasing difficulties in moving, breathing, swallowing, and speaking. In the last phase of an ALS patient's life it is necessary with respiratory therapy in order to breathe. In average an ALS patient lives 3 years from the time he or she gets the diagnose. The cause of the disease is still unknown and there is currently no treatment which can stop the progression of the disease. Former clinical studies have indicated that the innate immune system and in particular the complement system plays a significant role in the progression of ALS. The complement system, which is activated in cascades, is part of the innate system but participates in the innate as well as the acquired immune system. Former clinical trials have been characterized by limited knowledge about both the complement system as well as to how it is measured. Today it is possible to measure directly on the different components of the complement system and to understand its contribution to the overall immune response. It is also possible today to detect defects of the complement system. All these progressions are the foundation for this project which is carried out in close cooperation with one of the world's leading researchers in the complement system, professor Peter Garred from Rigshospitalet. The aim is to make a national research project about ALS in order to investigate the role of the innate immune system, and especially the complement system, in patients with ALS. In the long term the hope is, that this will lead the way to a targeted and effective medical treatment to the people affected by this grave disease.