A 6-month-old patient manifesting cold panniculitis had negative responses to tests for abnormalities of coagulation, serum proteins and immune response. Following application of ice, serial histopathologic studies were done at one-half, 6, 24, 48, and 72 hours, six days, and two weeks. These revealed a panniculitis at the dermal-subdermal junction with a predominance of histiocytes in the cellular infiltrate at 24 hours. The maximum reaction was seen at 72 hours. At two weeks the reaction had almost completely subsided. These changes paralleled the clinical course of the erythematous, indurated plaque which did not appear until 48 to 72 hours after insult, and then gradually subsided without any residual change. At 18 months of age his unusual sensitivity to cold disappeared.