The psychophysiological literature has often ignored possible differences in the effects of white noise and tone stimulation. Twelve undergraduate Ss presented with 10 white noise and 12 Ss presented with 10 tone stimuli of 5-sec duration, uncontrolled, fast rise time, and equal SPL (85 dB re 0.0002 microbars) showed large differences in heart rate (HR) response. Noise elicited a diphasic response of marked acceleration followed by deceleration and tone a triphasic response of deceleration-acceleration-deceleration. The short-latency acceleration following noise habituated rapidly although some acceleration persisted throughout the 10 trials. With stimulus repetition, the response to tone showed lessened deceleration and an insignificant increase in long-latency acceleration. It was suggested that stimulus onset characteristics determine the short-latency HR response and steady-state characteristics the longer-latency phases. The relationship to fast and slow components of startle was discussed as well as possible mechanisms that may account for the differing effects of noise and tone.