The pathologic condition of the spleen in sickle cell anemia is characterized by a series of progressive changes from congestive enlargement to fibrotic atrophy. The gross and microscopic appearances of spleens examined at different intervals in this process are varied and apparently dissimilar. The descriptions of the thirty-three spleens available in the literature1are mostly in the form of single case reports by different authors, and with few exceptions they are brief and lacking in essential details. It is difficult to obtain from these descriptions a clear concept of the sequence of events or a picture of the process as a whole. It is my purpose in this paper to describe the lesions of the spleen in sickle cell anemia, to trace the develop