Background: Interstitial granulomatous dermatitis is a histopathologic pattern with variable clinical appearance associated with autoimmune systemic diseases. The frequency of its different cutaneous expressions and its association with autoimmune diseases are not known. Objective: We describe the clinical, serologic, and histologic features in 17 patients with interstitial granulomatous dermatitis with a clinical presentation consisting of large erythematous plaques. Method: Skin biopsy specimens fulfilling criteria for diagnosis of interstitial granulomatous dermatitis were selected and correlated with the clinical and laboratory findings. Results: The study included 1 man and 16 women with multiple, asymptomatic, round to oval, erythematous plaques, most often on folds of the skin, in a bilateral and somewhat symmetric distribution. Most of patients had rheumatoid polyarthralgias along with various serologic abnormalities, often connected to collagen vascular diseases. Histologic examination disclosed a distinctive interstitial granulomatous dermatitis characterized by a diffuse infiltration of the interstitium by histiocytes with piecemeal fragmentation of collagen and formation of small granulomas around degenerative areas in concert with variable numbers of polymorphonuclear leukocytes sprinkled within the infiltrate. Churg-Strauss granulomas in miniature and flame figures were occasionally observed and indicated continued or increased activity of the associated autoimmune disease(s). Conclusions: Interstitial granulomatous dermatitis with plaques is a distinct entity with highly reproducible clinical and histopathologic features; recognition of these features identifies a patient who may have an underlying systemic autoimmune disorder. (J Am Acad Dermatol 2002;46:892-9.)