Alveolar macrophages (AM) from the beagle can release interleukin 1 (IL-1) by the exposures to dust particles. IL-1 activity was significantly detected after the exposures to silica and asbestos particles in vitro, and this induction was enhanced in the presence of LPS. This result indicates that AM may have an immunostimulatory effect in the lungs after the inhalation exposures to dust particles.