The aim of this study was to determine the localization and number of apoptotic cells in lung tissue and bronchus-associated lymphoid tissue (BALT) of newborns, young, and adult rats exposed to formaldehyde (6 ppm) or technical xylene (300 ppm) for 6 weeks (8 h/day). A total of 27 female Sprague-Dawley rats were used. Apoptotic cells were mainly localized around the bronchus and bronchioles and relatively less frequently on the walls of alveoli and interalveolar septa both in control and experimental groups. In the BALT, reactive cells were localized in the area under the epithelium and distributed homogenously within the lymphoid follicles. The numbers of apoptotic cells in the lung tissue including the BALT were significantly higher in young and adult rats exposed to formaldehyde and xylene than those detected in control groups.