Calciphylaxis (CPX), an uncommon syndrome characterized, in part, by progressive cutaneous vascular calcification, is seen principally in the setting of renal failure-associated hyperparathyroidism and is difficult to distinguish histologically from other microvasculopathies. We assessed histologic specimens from 13 cases of clinicopathologically classic CPX of the skin and reviewed documented histologic findings in the literature. Our series included 7 "early" and 6 "late" lesions (absence or presence of tissue necrosis, respectively). Histologically, early lesions were subtle and almost inapparent microscopically. Late lesions were easier to recognize because of obvious epidermal ulceration, dermal necrosis, and easily seen mural vascular calcification. The most common finding in both groups was acute and chronic calcifying septal panniculitis. Endovascular fibroblastic proliferation was more common in advanced lesions. Necrosis of dermal collagen was identified in only a few early lesions. Frank luminal vascular thrombosis was infrequent in both groups. The cited histologic findings largely were mirrored by those in the literature. Although they are relatively nonspecific when considered in isolation, the cited histopathologic features of cutaneous CPX allow for the diagnosis of this potentially lethal disorder when they are seen in combination with one another, particularly if detailed clinical data also are available.