We studied functional deterioration in adults with cerebral palsy working at community workshops throughout Japan by interviews and direct examinations. The incidence of functional deterioration was 36%, being higher among those with involuntary movements of the head and neck, abnormal movement patterns when moving and those with reported in poor work environment. In more than one-half case, deterioration was associated with inadequate in noise control, lighting, air circulation from the cooling and heating systems, height of the chairs and desks, and height of VDT screens. Though the factors intrinsic to cerebral palsy were often responsible for the functional deterioration, environmental factors were also significant. Studies on the work environment as well as medical evaluations are needed.