Two studies analyzed psychometric properties of the Spanish version of the NEO-FFI. First, 517 university students completed the original NEO-FFI (Costa & McCrae, 1992). Results showed an adequate factorial structure, high reliability index for the N, E and C factors, and acceptable for O and A. 8 items presented difficulties in their factorial position, discrimination power, or both. Second, 204 university students completed the NEO-FFI plus 16 additional items. As a result, 5 items were replaced and 3 neutralized. With those changes made, the reliability index rose to 0.70 throughout all the scales and the explained total variance percentage rose to 38.29.