In the present study, development of the lymphoid organs thymus, spleen, lymph node, palatine tonsil and peyer's patches were studied histomolphologically in developing fetuses. Thymus developed initially in the region of neck and then migrated to anterior mediastianum. Lymphocytes first appeared in the thymus at the 9th week, trabeculae developed from the 9th week onwards, lobulation started to develop at the 9th week and continued till the 12th week, corticomedullary differentiation was apparent during the period of 9th to 14th week, Hassell's corpuscles first appeared at the 15th week.
