A new, ten-item, self-rated depression scale, the Brief Depression Scale (BDS), was validated in 275 psychiatric in-patients and out-patients with depressive illness and anxiety disorders and a non-clinical sample of 50 subjects. The BDS showed satisfactory convergence with the interview rated Montgomery Åsberg Depression Rating Scale (rs = 0.72 and p < 0.001) and Hamilton Depression Rating Scales (rs = 0.70 and p < 0.001) and with the depression subscale of the self-rated Hospital Anxiety and Depression Scale (rs = 0.89 and p < 0.0001). The BDS had satisfactory internal consistency with a Cronbach's a-value of 0.86. The construct validity of the scale was assessed by principal components analysis and a two-factor solution was found in the clinical sample which explained 54% of the variance in the BDS total score. The sensitivity of the scale to clinical change in patients treated over an 8 week period was found to be satisfactory (as judged by the biserial correlation coefficient of change in BDS score with changes in other depression measures). The BDS had a sensitivity of 87% and specificity of 90% at a cut-off score of 19. The BDS is a brief, reliable and valid measure which may be useful in primary and secondary care settings as both a screening and outcome measure for depression