The impact of interviewer-effects on subjective evaluative criteria was examined in a randomized control group design (n = 26 x 2) of clients of sheltered living in Berlin-Spandau. The assessment of care and subjective quality of life showed that clients were more satisfied if they had been interviewed by their responsible caregivers compared to interviewers from other providers of the same region--unknown to the clients. Conductibility of interviews was independent of interview conditions. A systematic overestimation of satisfaction should be taken into account if responsible caregivers interview their own clients. Such data should not be used comparing different settings.