This study sought to characterize the nature of breakthrough pain experienced by 22 hospice patients and to assess the perceptions of their respective caregivers. Questionnaires were administered by trained hospice nurses to determine key elements of episodic pains in this home-based terminally ill population. Eighty-six percent of the patients surveyed experienced breakthrough pain, with an average of 2.9 episodes per 24-hr period and a mean pain intensity of 7 on a ten-point scale, compared with average baseline pain scores of 3.6 (daytime) and 2.6 (nighttime). Breakthrough pain episodes lasted 52 min on average, with a range of 1-240 min. The range of time to relief of breakthrough pains was 5-60 min, with a mean of 30 min. Caregivers' perceptions of the pain intensities, duration, amount of relief, and time to relief were much more likely to be inaccurate, and were usually underestimates. This study suggests that breakthrough pain is common in the hospice setting and that there is poor concordance between patients' self-reports and their caregivers' perceptions of these pains. It is concluded that the pharmacodynamics of currently available oral analgesics are not well-suited for breakthrough pain and that better communication between patients and caregivers may lead to more optimal pain management.