Although cross-sectional late-phase reinnervation in heart transplantation (HTx) recipients has been demonstrated by several earlier studies, early-phase successive analyses especially for parasympathetic reinnervation remain unknown. Successive heart rate variability (HRV) data calculated by the MemCalc power spectral density method were obtained from 16 non-rejection recipients 1-24 weeks after HTx. High frequency (HF) level representing parasympathetic magnitude increased significantly at 6 months after HTx (from 0.9�0.7 to 4.1�2.8 ms2*). Only intraoperative shorter cardiopulmonary bypass time (181�59 minutes) correlated with a higher level of HF at post-HTx 6 months among all baseline variables (r=-0.530*). Higher level of HF was associated with recovery of tachycardia at post-HTx 6 months (r=-0.514*). In conclusion, parasympathetic reinnervation emerges along with recovery of tachycardia< 6 months after HTx, which is accelerated by shorter intraoperative cardiopulmonary bypass time (* P< 0.05 for all).(Int Heart J 2014; 55: 440-444)