Summary TGF β stimulates human blood monocyte migration, with peak migratory response occurring consistently at a concentration of 16–100fg/ml. Checkerboard analysis revealed both chemotactic and chemokinetic components to this response. At higher concentrations (10–100pg/ml), TGF β stimulated expression of angiogenic activity by monocytes. While mRNA for TNF α was undetectable in resting monocytes, high steady state levels of TNF α mRNA were rapidy induced in TGF β-treated monocytes. TGF β is secreted by a number of neoplastic cells as well as normal cells such as platelets and lymphocytes. TGF β may recruit monocytes from the circulation, and subsequently activate them to express angiogenic activities such as TNF α, thus playing an important role in wound repair, inflammation and tumor growth.