Abstract：Porcine pulmonary alveolar macrophages (PAMs) were infected with A/Swine/Guangdong/1/2004, a swine influenza virus (SIV) isolate. Results showed that A/Swine/Guangdong/1/2004 was able to carry out productive replication in PAMs. DNA laddering in SIV-infected cells showed subdiploid DNA peaks at 24, 48, and 72 h post-infection by flow cytometry. Under light and electron microscopes, morphological changes in SIV-infected cells were observed, including cell shrinkage, plasma membrane blebbing, nuclear condensation, and cytoplasm vacuolization. These results indicate that SIV may induce apoptosis in PAMs in vitro, and apoptosis may play an important role in death of PAMs infected with SIV.