The traditional doctor-patient relation has become a great bioethical challenge due to the advances in science in recent years. This is particularly true when patients suffer diseases such as amyotrophic lateral sclerosis (ALS), a neurodegenerative disease with a relentless course and in spite of modern treatment 50% of the patients die within three years of first having symptoms of the disease. It therefore causes great psychological and social impact.To analyze the great bioethical challenge which arises when diagnosing and treating a patient with ALS.In this paper we analyze the doctor-patient relationship, the principles of doing no harm and of being beneficial, and more modern concepts such as informed consent, biomedical investigations and euthanasia, as well as the importance of palliative medicine and rehabilitation to alleviate suffering and improve quality of life. Biomedical investigations should conform to the relevant national and international rules. We discuss the right of patients to be given truthful information.We recommend better training of doctors in all aspects of attention to these patients, with emphasis on the diagnosis and importance of rehabilitation, palliative medicine and the management of psychological aspects. Biomedical investigations should fulfil current regulations. We recommend discretion, complete or partial, with regard to information given to the patients and their relatives so as not to cause despair.