Eighty-four nurse-patient dyads were studied to obtain descriptions of pain from medical, surgical and oncology patients experiencing pain. These descriptions were compared with the documentation of pain assessment recorded by the nurses providing care to these patients. Neither the descriptions of pain nor the amount of information documented about that pain differed significantly across the three groups. For each group, nurses documented significantly less than 50% of what the patients described. Inadequate documentation of pain assessment has legal and continuity of patient care implications.