Objective: The Pain Level Memory Device (PLMD) is an instrument which patients can use to record their subjective level of pain. The usefulness of the PLMD on both medical staffs in managing cancer pain and the independence of patients were examined in this study. Method: Ten participants, inpatients at Nagoya University Hospital prescribed opioid drugs for cancer pain, were selected and asked to input any change in their pain level into the PLMD for a 14 day period between February and April 2005. A graph of the resulting data was printed and given to both the patient and medical staffs. And a questionnaire evaluating their experience with the PLMD was developed and administered to both. Relationships between the frequency of use of the PLMD and item-scores on the questionnaire were investigated. Results: The median number of inputs into the PLMD was 4.5 (range: 0.5-11) per day. High usage of the PLMD and each high score for the questionnaire items "The PLMD helped assessment of pain (p<.05)" and "The patients satisfaction with pain control improved (p<.05)" were strongly correlated. Spearman's rank correlation coefficient showed a relationship between the median number of inputs and the questionnaire items, "I used the PLMD whenever I intended to (r=.80, p<.01)", ""I saw graphs (r=.78, p<.01)", "I discussed graphs with my doctor (r=.70, p<.05)", "I felt that I participated in my pain management (r=.82, p<.01)", and "I would recommend the PLMD to other patients (r=.80, p<.01)". Conclusion: These results suggested that the PLMD could assist medical staff in the control of cancer pain and support the independence of patients.