Utilizing our chronic denervation animal model (Tong et al. Lab. Animal Sci. 1995,45:398-403, J. Auton. Nerv. Syst. 1997, 64:162-165), we examined the effects of denervation on the ECG and heart rate before, during and after stimulation of the high pressure baroreceptors with phenylephrine (PE:30ug/kg). Piglets (5-7 days old) were separated into 3 groups: sham-operated controls (C), left or right stellectomy. Piglets were studied until 8 wks of age. Recordings of ECG were obtained during 1-2 hr intervals during resting or sleeping conditions which permitted more detailed analyses of the ECGs. Poincare plots were used to determine differences in R-R and QT intervals with age between the 3 groups. No differences were noted between C and denervation groups until 1 week postsurgery (approx. 10 days postnatal age). At 8 weeks of age under light Saffan anesthesia, we examined the effects of acute elevation of blood pressure (AoP) on the ECG. The degree of AoP elevation following PE were equivalent in both C and denervation groups. Marked cardiac dysrhythmias occurred in response to elevation of AoP in the chronic denervated animals as compared to C. Since many stimuli can occur to raise pressure naturally (not just under experimental conditions), it is quite possible that such dysrhythmias might occur in those animals found dead of no known cause(J. Auton. Nerv. Syst., 1997). Such dysrhythmias are of particular interest given the increase in AoP at onset of wakefulness. These results further confirm the usefulness of our model of SIDS.