In this study, we generated 40 somatic cell cloned (scNT) piglets. Of these, five piglets were stillborn, 22 scNT piglets died suddenly within the first week of life, and 1 piglet died after 40 days. Twelve scNT piglets are still healthy. The birth weights of compromised scNT piglets in comparison with those of normal scNT piglets are significantly reduced (0.80 +/- 0.29 vs 1.27 +/- 0.30 kg, p < 0.05), in spite of longer gestation (114 versus 120 day). Significant findings from histological examinations showed that approximately 25% (7/28) of scNT piglets showed severe congestion of lung and liver or neutrophilic inflammation in brain indicating that unexpected phenotypes can appear as a result of somatic cell cloning. Two-dimensional gel electrophoresis experiments revealed changes in the responses of several detoxification-related proteins related to stress and inflammation and found significant alterations in myocardium-specific proteins, indicating hemodynamic disorder. scNT piglets that survived to adulthood did not show any abnormality except skin and hair color depigmentation. The present study suggests that cerebromeningitis and hemodynamic disorder are a major risk factor for sudden early death of scNT piglets. Although we cannot completely exclude the possibility that scNT piglets are susceptible to specific respiratory infections, our data suggests that the early death of scNT clones is due to cardiopulmonary functional abnormalities and cerebromeningitis.