This study investigated the effects of biofeedback/self-management training on heart rate variability (HRV) in six sudden cardiac arrest survivors. The physiological-theoretical basis of the training was cognitively inducing respiratory sinus arrhythmia. Power spectral analyses and nonspectral analyses (Kleiger, Magid, SCANN, BB50 measures) of HRV measured before and after 5 weeks of biofeedback training are described. The posttraining Kleiger measure of mean HRV increased compared to the pretraining mean HRV (159 +/- 37 ms vs 147 +/- 38 ms). After training, the high frequency components (0.27-0.30 Hz) of the power density spectra were markedly increased, suggesting an increase of respiratory-driven parasympathetic activity. After training, the low frequency components (0.05 Hz) were slightly decreased, suggesting a decrease in sympathetic activity. The increases noted in the high frequency components were more striking during 9 hours at night than during the day. These data indicate that subjects who have had sudden cardiac arrest can, through biofeedback/self-management, cognitively increase their HRV over a 5-week period, consequently increasing parasympathetic activity.