The definition of rehabilitation is debated, but the true sense of the word is "reinstatement in dignity." There is often a need for rehabilitation after diseases and injuries. Rehabilitation is founded on the individual's right to participate in society and to have equal opportunities in general, and can be considered both in a medical and a sociological perspective. WHO has developed "International Classification of Functioning, disability and health"-ICF. ICF reflects an understanding of function and disability in a bio-psychosocial model. The issues discussed in this article will be limited to rehabilitation within the Norwegian healthcare system. Rehabilitation is based on the individual's loss of function, irrespective of the injury or disease, and should focus on resources. Its main issue is the subject's own goals and wishes with respect to quality of life and total life situation. Many groups that have, or are in danger of acquiring reduced function are in need of rehabilitation, if this can prevent or reduce loss of function or participation. The measures taken can be directed over a wide spectrum, directed towards function and activity, and often with participation in a variety of life aspects as the main goal. Rehabilitation is presented with many challenges caused by the general development in society, including implementation of the medical and technological development and demand of scientific documentation.