The possibility of the penetration of pollen grains into the tracheobronchial tree is still a controversial question. To investigate this phenomenon further two different approaches were conducted: 1) Acetolysis (acidic degradation of organic constituents) of mucosal samples from different levels of the pig respiratory tract showed that specific (plane tree) inhaled pollens were not found beyond the main bronchi. 2) In contrast, a noticeable number of pollens were present in acetolyzed residues of lung surgical samples; this was shown to be due to contamination. In the first approach this problem was avoided; however, the analysis of surgical samples could be a valuable technique if suitable controls were included.