ABSTRACTHeart rate is a widely‐used dependent variable in psychophysiological research. A survey of articles published inPsychophysiologyduring 1978, 1980, 1982, and 1984 revealed wide variation in procedures for obtaining “resting’ measurement of heart rate prior to administration of other stimuli or tasks. Duration of the baseline period at the beginning of 35 reported investigations was negatively correlated (r=−.64) with heart rates. Variations in duration of baseline measurement may influence some kinds of Type II errors such as the likelihood of detecting relative group differences in heart rate during more active stimulus‐presentation or task periods. Alternative procedures (a minimum 15‐min adaptation period prior to assessment, individualization of duration of baseline assessments) ar