Blood pressure (BP) and heart rate (HR) are influenced by the sleep-wake cycle, with relatively abrupt falls occurring in association with sleep onset (SO). However, the pattern and rate of fall in BP and HR during SO, and the processes that contribute to the fall in these variables have not been fully identified. Continuous BP and HR recordings were collected beginning 1 h before lights out (LO) until the end of the first NREM sleep period in 21 young, healthy participants maintained in a supine position. Five consecutive phases were defined: 1) the 30 mins of wakefulness before LO; 2) LO to stage 1 sleep; 3) stage 1 to stage 2 sleep; 4) stage 2 sleep to the last micro-arousal before stable sleep and; 5) the first 30 minutes of undisturbed stable sleep. The data were analysed on a beat-by-beat basis and reported as 2 min periods for phases 1 and 5, and 10% epochs for phases 2, 3 and 4 (as participants had variable time periods in these phases). The level of baroreflex (BR) activity was assessed by the sequence technique and an autoregressive multivariate model. Further, during phases 3 and 4, the BP and HR responses to arousal from sleep were determined. There were substantial falls in BP and HR following LO before the initial onset of theta activity (phase 3), and again following the onset of stable sleep after the cessation of spontaneous arousals. During phases 3 and 4 when there were repeated arousals from sleep, the fall in both variables was retarded. Further, both the rate and magnitude of the fall in BP were negatively associated with the number of arousals during phases 3 and 4. There was a small increase in the sensitivity of the BR and indirect evidence of a substantial fall in its set point.