The NOD mouse develops spontaneous autoimmune lesions in the lacrimal and salivary glands, besides a well characterized T cell-mediated autoimmune pancreatic beta cell lesion. We report unique pathological findings developed in the lacrimal glands as an autoimmune dacryoadenitis of NOD mice in contrast to those found in the salivary glands and pancreas. A high incidence of autoimmune lesions in the lacrimal glands was observed exclusively in male NOD mice at any age. Histology of autoimmune dacryoadenitis in male NOD mice showed severe destructive changes compared with those observed previously as an autoimmune lesion in the lacrimal glands. Castration in male NOD mice significantly decreased the incidence of autoimmune dacryoadenitis, and testosterone treatment with castration also increased the incidence of autoimmune lesions. Oestrogen treatment with castration did not increase the incidence, but tamoxifen treatment without castration significantly increased the incidence of autoimmune dacryoadenitis in NOD mice. In addition, we detected up-regulation of local cytokine genes (IL-1beta, tumour necrosis factor-alpha (TNF-alpha), IL-2, interferon-gamma (IFN-gamma), IL-6, IL-10, and IL-12 p40) during the course of autoimmune dacryoadenitis. These data suggest that in spontaneous autoimmune dacryoadenitis of male NOD mice there may be an intimate relationship with sex steroids, particularly testosterone, in the development and progression of autoimmune lesions, and autoreactive Th1 cells secrete up-regulated cytokine genes, including IL-10 and IL-12.