The histological and ultrastructure of spleen of the maculated toad, Bufo regularis (amphibians) were studied.  Splenic structure is differentiated into red and white pulps and connective tissue.  The red pulp is formed of sinusoids, arterioles, lymphocytes, reticular cells, macrophages, plasma cells and granular leucocytes, as well as thrombocytes in the sinusoids, whereas, the white pulp consists of arterioles surrounded by lymphocytes, reticular cells and some plasma cells. Pigment cells were also noticed in red and white pulps. In conclusion: the discussion of this investigation with other studies of  higher vertebrates (amniotes) explained that the organization of the spleen structure in the maculated toad, Bufo regularis upgrade from simplicity to complexity and is considered as an intermediate condition between lower vertebrates and those of amniotes.