An acute inflammatory response was elicited in the lungs of strain 2 and 13 guinea pigs following immunization and aerosol challenge with ovalbumin. The pulmonary inflammatory response, characterized by hemorrhage and influx of inflammatory cells, progressed from initiation at 12-hours postchallenge through resolution at 96-hours postchallenge. Inflammatory and immunoregulatory cells, recovered by bronchoalveolar lavage, showed quantitative changes in their relative contribution to the bronchoalveolar cell infiltrate over the course of inflammation. Changes in concentrations of macrophages and T cells, in particular, are discussed in terms of their possible contributions to initiation and resolution of acute pulmonary inflammation.