Since existing depression scales were designed for assessment of depression in non-psychotic populations, such scales have items which do not distinguish depressed from non-depressed psychotic subjects. The authors describe a new scale, the Calgary Depression Scale, which was designed for the assessment of depression in schizophrenia. The scale was derived from two existing scales by factor analysis and reliability analysis. It has been further tested in two new samples. In the first it has been shown to be reliable, congruent with a self-report scale and valid. In the second sample it has been shown that there is no overlap with negative or extrapyramidal symptoms.