Erythrodermic psoriasis (EP), 1 of the most rare and severe forms of psoriasis, is characterized by general erythema with silvery scales. Systemic vasodilatation in EP is potentially life-threatening, however, the degree and extent of inflammation in subcutaneous tissues are difficult to estimate accurately using standard skin inspections or ultrasound examinations. Computed tomography can be a useful modality in solving this problem. The authors report a case of EP. Sequential contrast-enhanced whole-body computed tomography before and after treatment with a tumor necrosis factor-α inhibitor (infliximab) visualized the inflammation and the effect of the treatment.