Lack of insight into mental disorder is a frequent phenomenon in patients affected by a psychotic disorder and can be an important predicting factor involving the course of the disease mainly regarding compliance with treatment. The aim of the present study was to validate the Portuguese version of the Marková and Berrios Insight Scale, a self-report instrument that allow us to evaluate insight into psychotic illness. After a translation-back translation process, the Portuguese version of the scale was administered to a sample of 83 psychotic patients (DSM-IV). The results demonstrated that the Marková and Berrios Insight Scale achieved a excellent viability, internal reliability (a = 0,80). These coefficients were similar to those found by the researchers who developed this scale. The Marková and Berrios Insight Scale has proven to be easily applied and deemed an useful and valid instrument in researches involving psychotic subjects.