We report on the process of adaptation into Spanish of the Rotterdam Symptom Check List (RSCL). The original version was translated and back-translated by professional bilingual translators. A quantitative rating method was used to select the items to include in the final Spanish version. Validity (discriminant and construction) and reliability were test in 118 terminal cancer patients. In addition to the RSCL the Nottingham Health Profile (NHP) and the Karnofsky Performance Status (KPS) were used. The RSCL showed different ratings on all scales according to the functional level of the patients. The scales were moderately to highly correlated with the NHP (from 0.48 to 0.71). Internal consistency, measured by Cronbach's alpha coefficient ranged from 0.74 (physical) to 0.90 (activity). Twenty-four hours test-retest intraclass correlation coefficient ranged from 0.71 to 0.88. The results of this study suggest that the Spanish version of the RSCL is conceptually equivalent to the original. More research is needed to assess the responsiveness of the version before using it in clinical trials.