Angioimmunoblastic T-cell lymphoma is a type of peripheral T-cell lymphoma that is clinically characterized by high fever and generalized lymphadenopathy with or without cutaneous involvement. A 55-year-old Japanese man presented with red papular lesions on the trunk and limbs, oedema, and generalized lymphadenopathy. Histological findings in the lymph nodes showed destructive germinal centres, proliferation of arborizing postcapillary venules, and atypical medium-sized lymphocytes. The cutaneous lesions also contained atypical lymphocytes. Immunohistochemical studies indicated that the neoplastic cells were mature CD4+ T lymphocytes. Southern blot analysis detected a clonal expansion of T-cell receptor β. Based on these findings, a diagnosis of angioimmunoblastic T-cell lymphoma with cutaneous infiltration was made. Despite systemic chemotherapy, the disease exhibited a high level of activity and continued on a fatal course. An analysis of gene expression profiling using complementary DNA microarrays revealed significant expression of some chemokines and cytokines, e.g. secondary lymphoid tissue chemokine, macrophage inflammatory protein (MIP)-1β, MIP-3α, MIP-3β, B-lymphocyte chemokine, interleukin-16 and tumour necrosis factor-β, and an apoptosis-inhibitory protein (FLICE inhibitory protein) in the affected lymph nodes. Profiling of gene expression patterns for a variety of genes in additional cases may be helpful in determining which factors predict the biological and clinical behaviour of angioimmunoblastic T-cell lymphoma or other aggressive malignant lymphomas.