Vitritis, the presence of leucocytes in the acellular ocular vitreous, often accompanies ocular vasculitis (V). Non-cultivatable intracellular mollicutes (M), i.e. cell wall deficient bacteria, readily identified by transmission electron microscopy (TEM), are well known plant vascular pathogens. Recently similar intracellular polymorphonuclear leucocytes (PMNL) and lymphocytes (L) parasitising/destroying and mouse ocular and lethal systemic V producing M-like bacteria were reported to be a common cause of human ocular V. In this TEM restudy of 8 human and 3 mouse VM induced chronic ocular V materials severe nuclear and cytoplasmic alterations associated with generalized cytoskeletal nuclear-anchoring 0.005-0.010 micron particles, 0.01-0.05 micron diameter branching filaments and tubules, and trilaminar membrane bound complex internal structure containing 0.1-1.9 micron spherules, all indistinguishable from VM, were observed within 1-3% of the monocytes in all 11 specimens. The results indicate that VM also parasitise and destroy both human and mouse monocytes. VM induced alterations in monocytes, PMNL, and L are compared, and the monocyte nuclear damage/Rifampin beneficial effect relationship in VM induced ocular V is discussed.