The fat body is a loosely packed tissue distributed throughout the body cavities of millipedes. The main function of this tissue is the storage of lipids, glycogen, proteins and uric acid and also serves as a site for the permanent storage for excretion products. In this work, we examined the ultrastructure of the mineralized bodies found in the fat body of the millipede Rhinocricus padbergi. The mineralized bodies were spherical bodies that varied in structural organization within a single cell: some consisted of several concentric layers of amorphous material while others were surrounded by a layer of electron-dense material intimately associated with the surrounding membrane. The histochemical and ultrastructural results suggested that these mineralized bodies are involved in the accumulation of calcium and uric acid. The large number of these structures found in the fat body of millipedes may be a consequence of these animals´ diet since they overturn soil rich in large amounts and/or variety of minerals. As in other organisms, uric acid probably accumulates as the metabolic product of the degradation of nucleic acids derived from autophagy of the rough endoplasmic reticulum due an earlier massive protein synthesis, but may also be extracted from the hemolymph.