Renal granulomas are a relatively infrequent finding in the kidney biopsy. They have been described in a number of syndromes such as Wegener's granulomatosis, anti-GBM glomerulonephritis, and sarcoidosis, and are commonly believed to be indicative of a fulminant clinical course. In leading textbooks, diverse definitions of renal granulomas are presented, which has led to controversies in identifying them. This, in combination with their rare occurrence, makes it difficult for the general pathologist to identify them. We present the clinical data of 16 patients with renal granulomas, from a total group of 157 patients with systemic vasculitis. Their renal functioning was not significantly different from the other 141 patients in whose renal biopsies renal granulomas were present. Furthermore, we present two practical definitions for the recognition of renal granulomas in the kidney biopsy, and we show a number of examples of their various histopathological shapes.