Pulmonary macrophages (Mphi) increase in tissue and bronchoalveolar lavage (BAL) fluid during inflammation caused by bleomycin (BLM). This study demonstrates that increasing numbers of exudate Mphi in BLM lung injury exhibit dendritic cell (DC) features. After the intratracheal administration of BLM (0.075 U), adherent mononuclear cells from the bronchoalveolar lavage fluid (BAMC) of C57BL/6 mice were characterized for morphology, immunophenotype, and accessory cell activities. At day 7 post-BLM, 48% of CD11b+ BAMC displayed features of DC differentiation, as judged by dendritic morphology, expression of class II MHC, 33D1, Factor XIIIa, CD80, and CD86 antigens, and the ability to support a primary allogeneic lymphocyte response (MLR). After BLM treatment, CD11b+ peripheral blood monocytes also showed increased expression of 33D1, Factor XIIIa, CD86, and the ability to stimulate an MLR. We conclude that inflammatory DC with immunophenotypic features of monocyte-derived DC increase in the peripheral blood and lung after an inflammatory stimulus.