Bovine phagocytic cells (polymorphonuclear granulocytes, blood monocytes and alveolar macrophages) were treated in vitro with homogeneous, recombinant DNA produced bovine alpha-1 interferon (IFN-alpha 1). The effects seen comprised of enhanced bacterial uptake by all three cell types and increased Fc receptor activity in alveolar macrophages, inhibition of both directed and random migration of monocytes and polymorphs, increased enzyme release or inactivation, increased hydrogen peroxide generation, and decreased superoxide anion release by alveolar macrophages and polymorphonuclear leukocytes. These effects were dose- and time-dependent, the kinetics varying for the different cell types.