This study of the clinical picture in 40 consecutive cases of pernicious anemia points out a common failure to suspect the disease even though it may have been present in a well developed form. The disease rarely presented in what is often considered to be a textbook manner. Often the presenting manifestations were those of more common diseases or were due to aggravation of underlying heart disease. The chances of an early diagnosis will be enhanced if the physician will think of pernicious anemia as a systemic deficiency of vitamin B12 which may overtly involve several body systems singly or in a great variety of combinations. The presenting symptoms may be due to involvement of 3 of the cell types of the blood, the brain, the gastrointestinal tract from tongue to colon, the spinal cord or peripheral nerves. There is no single typical manner of presentation.