Undertreatment of cancer pain is widely recognized. This study sought to determine if inadequate communication about pain intensity between health care providers and their patients could represent a significant factor interfering with the control of cancer pain. One hundred and three consecutive patients with solid tumors and normal mental status examinations were screened within 48 hr during two study periods. The intensity of patient pain was assessed using a visual analogue scale (VAS) which was given to the patient, his/her primary care nurse, house officer and medical oncology fellow. Sixty-three percent of the patients were taking narcotic analgesics on admission to the hospital. Although there was a correlation between patient and health care provider ratings for the entire group, no statistically significant correlation between the patient's VAS pain score and that of his/her nurse, house officer, or oncology fellow was present in the 44 patients with VAS greater than or equal to 4.0. Agreement between patient and caregiver VAS scores was also examined. When patients rated their pain from 7-10 on the VAS scale, nurses, house officers, and oncology fellows would place their rating of the patient's pain in this range 7%, 20%, and 27% of the time, respectively. Improved correspondence was noted with lower patient VAS scores. This study demonstrates that health care provider impressions of patient pain are often quite different than those of the patient and that these discrepancies are most pronounced in patients with significant pain. The routine use of pain assessment tools, such as the VAS, could enhance patient-caregiver communication and improve care for patients with cancer pain.