Abstract: Compounds of submicromolar concentrations of a histone deacetylase inhibitor, useful as anti-fibrotic agents. The compounds strongly inhibit three main features of myofibroblastic differentiation of cultured hepatic stellate cells and of skin fibroblasts: (1) synthesis of collagens type I and III, the predominant collagens in fibrosis of liver and other organs; (2) cellular proliferation; and (3) expression of smooth muscle .alpha.-actin, a marker for activated myofibroblasts. Preferred compounds include trichostatin A or a pharmaceutically acceptable salt thereof, and sodium butyrate.