This study tested the hypothesis that changes in bronchoalveolar lavage (BAL) inflammatory cell profiles reflect the clinical progress of patients with cryptogenic fibrosing alveolitis (CFA) when followed for substantial periods of time with or without any form of treatment. Two or more bronchoalveolar lavages (mean, 3; maximum, 5) were performed on each of 32 patients who were followed for periods as long as 7 yr (mean, 2.5 yr, median, 4 yr). The majority were studied before and during treatments with prednisolone alone or with prednisolone and cyclophosphamide. A total of 90 lavages were performed, and the changes in BAL inflammatory cell percentage counts were compared with defined categories of clinical progress. At initial lavage, 97% of the patients had an increased percentage of at least 1 BAL cell type. On follow-up, 12 patients showed definite and sustained clinical improvement, and their serial lavage cell counts tended to return towards normal. Falls in neutrophils were significant in patients responding to prednisolone, whereas falls in eosinophils were significant in those responding to cyclophosphamide. By contrast, in patients who failed to improve, neutrophil and eosinophil counts tended to remain elevated. However, several nonresponders appeared to have clinically stable disease, demonstrating that persisting granulocytes are not necessarily paralleled by clinical deterioration. Consecutive BAL cell counts in the pair of samples before and after introduction of prednisolone showed no overall change in any lavage cell type to suggest that the drug has a general effect independent of clinical progress. A similar comparison for cyclophosphamide showed falls in eosinophil percentage counts, but these were mainly responders.(ABSTRACT TRUNCATED AT 250 WORDS)