The TGF-beta family of cytokines are ubiquitous, multifunctional and essential to survival. They play important roles in growth and development, inflammation and repair and host immunity. The mammalian TGF-beta isoforms (TGF-beta 1, beta 2 and beta 3) are secreted as latent precursors and have multiple cell surface receptors of which at least two mediate signal transduction. Autocrine and paracrine effects of TGF-beta's can be modified by extracellular matrix, neighbouring cells and other cytokines. The vital role of the TGF-beta family is illustrated by the fact that approximately 50% of TGF-beta 1 gene knockout mice die in utero and the remainder succumb to uncontrolled inflammation after birth.