We studied the alterations induced by acute experimental extrinsic allergic alveolitis (EAA) on bronchoalveolar cell population in smoking and nonsmoking guinea pigs. Sixty-two animals divided into 3 groups were studied: Group 1 (17 animals), controls; Group 2 (21 animals), extrinsic alveolitis; Group 3 (24 animals), cigarette smoking and alveolitis. Bronchoalveolar lavages (BAL) were performed on Days 1, 19, and 44 for all animals. Group 3 animals had a fourth lavage before starting cigarette smoking, that is, 28 days before the beginning of the antigen injections. The other lavages were as for the other groups. BAL results on Day 1 were similar for each group. Cigarette smoking per se did not modify BAL in Group 3. EAA induction resulted in a large increase in all BAL cells, especially neutrophils of recovered fluid, which increased from 38 x 10(3) to 1,474 x 10(3) ml-1 (p less than 0.01) in Group 2 and from 58 x 10(3) to 740 x 10(3) in Group 3 (p less than 0.01). After maintenance, BAL neutrophils.ml-1 decreased to 444 x 10(3) in Group 2 (p less than 0.01), but stayed the same in Group 3: 973 x 10(3). After EAA induction, BAL neutrophils.ml-1 were higher in Group 2 than in Group 3 (p = 0.039); however, Group 2 had less neutrophils.ml-1 than Group 3 (p = 0.035) after EAA maintenance. We conclude that EAA results in a neutrophilic alveolitis and which can be evaluated by sequential BAL, and that cigarette smoking decreases the initial neutrophilic response and retards the eventual recovery during maintenance injections.