OBJECTIVES: Cognitive and sensory difficulties frequently jeopardize informed consent of frail elderly patients This study is the first to test whether preliminary research experience could enhance geriatric patients' capacity to consent. DESIGN/SETTING: A step-wise consent procedure was introduced in a study on fluid balance in geriatric patients. Eligible patients providing verbal consent participated in a try-out of a week, during which bioelectrical impedance and weight measurements were performed daily. Afterwards, written informed consent was requested. Comprehension, risk and inconvenience scores (ranges: (...) 0-10) were obtained before and after the try-out by asking ten questions about the study's essentials and by asking for a risk and inconvenience assessment on a ten-points rating scale. SUBJECTS AND RESULTS: Seventy of the 78 eligible subjects started the try-out and 53 (68%) provided written consent. The comprehension score increased from 5.0 (+/- 2.3) to 7.0 (+/- 1.9) following the try-out (P < 0.001). The number of subjects capable of weighing risks and inconveniences increased from 32 to 48 (P < 0.001). CONCLUSIONS: Research experience improved the capacity to consent, still enabling an acceptable participation rate. Therefore, experienced consent seems a promising tool to optimize informed consent in frail elderly subjects. (shrink)