Intravascular lymphoma (IVL) is a rare type of extranodal lymphoma in which the lymphoma cells proliferate exclusively in the lumina of small vessels. The diagnosis of IVL requires histological confirmation. Although random skin biopsy from healthy-appearing skin in patients with suspected IVL appeared to be useful, the sensitivity of this method for the diagnosis of IVL remains unknown. We performed a random skin biopsy from 12 consecutive cases of IVL diagnosed at our institution over the past 4 years and evaluate its relevance of clinical and laboratory characteristics, presence or absence of skin lesions, and bone marrow involvement. All 12 patients were diagnosed antemortem by either random skin biopsy or bone marrow biopsy and treated with rituximab-containing chemotherapy. Random skin biopsy was performed in all 12 patients, and the results were positive in ten patients (83.3%). Erythematous skin lesions were seen in 3 of 12 patients, but biopsy was positive for lymphoma lesion in two patients. Bone marrow invasion was seen in 11 of the 12 patients (91.6%) by bone marrow smear and/or flow cytometric analysis, but was detected in only half of the patients by trephine biopsy. We concluded that random skin biopsy from normal-appearing skin is highly sensitive in the diagnosis of IVL comparable to bone marrow trephine biopsy. It should be performed irrespective of the presence or absence of skin lesions in patients who were suspicious of IVL.