The aim of the study was to compare the results of routine counts of percentage of BAL macrophages, using morphological differential staining method--Pappenheim stain (M) and staining for nonspecific esterase activity (E) with those obtained by APAAP technique, using specific for monocytes (macrophages monoclonal antibodies (Ki-M1) and the complex APAAP (alkaline phosphatase--mouse anti alkaline phosphatase complex). The mean counts were comparable, although different criteria of estimation were used. Significant differences were seen in smokers when the criteria were based on morphology and expression of surface antigens. The results indicate that correct estimation of macrophage counts and their characteristics (enzymatic activity, expression of surface antigens) can only be made using many methods based on various criteria of estimation.