Spiral shaped bacteria present in blood smears and bone marrow of a sick rhinoceros iguana were examined by light and electron microscopy. The organisms averaged 10 micron in length and had at least three spiral turns. The cell contained nuclear areas, vacuoles and ribosomes, except at the poles where there was a virtual absence of organelles. The bacterium was found by a cell membrane, cell wall and enveloping sheath. "Blebs" were present with regularity on the cell surface. About 14 flagella were present at each pole, and at these sites there was a specialized thickening of the cell membrane. Organisms were present within a phagocytic vacuole of macrophages in the blood and bone marrow, and often these engulfed organisms were degenerated. The taxonomic position of the bacterium is unknown.