Vaginal photoplethysmography was utilized in combination with standardized sleep-recording procedures to investigate changes in vaginal pulse amplitude (VPA) during both waking and sleeping conditions in low- and high-arousability females (n = 10 per group), as classified by the Sexual Arousability Inventory. Based upon previous research, it was predicted that both groups would exhibit similar mean levels of VPA during waking exposure to erotic stimuli and during various stages of sleep. Despite hypothesized physiological similarities between groups, the low-arousability group was expected to subjectively report less arousal during the waking erotic conditions.