Morphometric studies of pulmonary airways and arteries can be laborious and time consuming. In order to see whether the effort involved could be reduced in some cases, data obtained from axial pathways of bronchopulmonary segments or lobes were compared with the mean total data obtained from four lungs. It was concluded that axial pathway data classified by generations could be compared between lungs only if the same segment or lobe was used from each individual. Such data are usually not representative of the total structure. Data from axial pathways of segments or lobes which have been classified by Horsfield orders can be pooled, and the mean values thus obtained are fairly close to the mean values obtained from the total data.