While the impact of mentally ill patients' perceptions of their key relatives' expressed emotion is well examined with regard to relapse, there is a paucity of evidence concerning the impact on their key relatives' burden. The present study aims to evaluate the relative prognostic value of expressed and perceived emotion on caregivers' stress outcome within a 3-year follow-up period. Yearly follow-up data of the key relatives of 16 first-hospitalized schizophrenic and 34 depressed patients were available including expressed and perceived emotion and different dimensions of caregivers' stress outcome: objective and subjective burden, well-being, psychological symptoms and subjective quality of life. Multiple linear regression analyses were computed to assess the relative impact of expressed and perceived emotion. All dimensions of burden were significantly and consistently correlated with caregivers' expressed emotion and patients' perceived criticism on the bivariate level. On the multivariate level, however, expressed criticism appeared to be the most relevant predictor, followed by perceived resignation. Data indicate that the impact of the patients' perceived criticism on caregivers' stress outcome is limited. More attention should be paid to patients' perceived resignation which may be an unidentified stress contributor for caregivers so far.