Counting of inflammatory cells in human airway biopsy specimens is difficult because immunopositive cells are present in varying density in lung tissue. The goal of our study was to assess the minimal amount of tissue that is necessary for the counting of constant cell numbers. In bronchial biopsy specimens from 5 healthy controls and 5 patients with asthma, we evaluated 20 successive areas of submucosa 0.1 x 0.1 mm in size. We recorded positive and negative changes of more than 10% in the counted numbers of CD4-, CD8-, and EG2-positive cells. We demonstrated that tissue 1.0 x 0.1 mm in size, along 1-mm basement membrane, is sufficient to obtain constant cell numbers.