The Edmonton Symptom Assessment Scale (ESAS) is simple and easy to use with cancer patients. This study was planned for the purpose of adapting and determining the validity and reliability of the ESAS for Turkish culture. The study was conducted in outpatient and inpatient chemotherapy units at a university hospital between December 2004 and February 2005. A total of 113 cancer patients participated in the research. Written permission to conduct the research was obtained from the facility and verbal and written consent was obtained from the patients. Research data were collected using a questionnaire, the ESAS and the Rotterdam Symptom Checklist (RSC). In the ESAS validity study, language validity, content validity and criterion-related validity were tested. In the reliability study Cronbach's alpha and item-total score correlation were calculated. The patients' mean age was 48.86±13.18. The Pearson product moment correlation coefficient between the ESAS and RSC scores was calculated to be r=0.75, p < 0.05. A Cronbach's alpha coefficient of 0.77 was determined for the ESAS. The lowest item-total correlation on the ESAS (r=0.30, p <0.05) was for item 10 (other, constipation) and the highest (r=0.62, p <0.05) was for item 1 (pain). The Turkish version of the ESAS was determined to be a valid and reliable tool for use in Turkish individuals with cancer. [Turk J Cancer 2008;38(2):62-67]