Claw biopsy samples of 11 dogs with lupoid onychodystrophy were evaluated. They were stained with hematoxylin and eosin and with antibodies against CD 3 as a T-cell marker, BLA 36 and HM 57 (CD 79alpha) as B-cell markers, and lysozyme, Mac 387, and major histocompatibility complex (MHC) class II as a marker for histiocytes using an immunoperoxidase and avidin-biotin technique. Inflammatory cells were counted in five high-power fields. The inflammatory infiltrate comprised predominantly B cells and T cells. Macrophages were typically only present in small numbers. CD 3, BLA 36, lysozyme, and MHC class II preserved significant antigenicity during formalin fixation and short decalcification for 24-48 hours, whereas CD 79alpha and particularly Mac 387 seemed to be more susceptible to denaturation by the decalcification process.