This report shows the quantitative time-course profiles of transpulmonary migration of polymorphonuclear leukocytes (PMN) and the adhesive interaction of alveolar macrophages to the alveolar surface in response to intratracheally (i.t.) instilled endotoxin. Groups of mice received i.t. instillation of lipopolysaccharide (LPS), and free cells in the bronchoalveolar lavage (BAL) fluid were counted. PMN remaining in the lung tissue after the BAL procedure were also enumerated following enzymatic tissue digestion. Recovery of macrophages from the alveolar space by BAL was significantly decreased at 0.5 and 2h post i.t. instillation and returned to the control value after 5h, suggesting that alveolar macrophages became adhesive to the alveolar wall in response to LPS. Neither BAL nor lung tissue-associated PMN were increased until 0.5h post i.t. instillation of LPS. The lung tissue-associated PMN peaked at 2h, while the number of BAL PMN peaked at 5h post instillation. Furthermore, although the number of BAL PMN remained at the maximum value even at 24h post i.t. instillation of LPS, the lung tissue-associated PMN returned to the control level at this point. These results suggest that (1) the adhesive interaction of alveolar macrophages to the alveolar surface increased rapidly (<0.5h), (2) accumulation of PMN in the lung occurred later than the adhesion of alveolar macrophages (0.5 to 2h) and (3) transpulmonary infiltration of PMN was completed within 24h following i.t. instillation of LPS.