The objective of this study was to test whether the utilization of Minimum Data Set-Home Care (MDS-HC) as a case finding instrument for Chinese attenders of elderly health centres in Hong Kong had a beneficial impact on the physical and mental health status of those older clients. The dependent variables were 13 outcome variables measuring different dimensions of participants' physical and mental health status. Using a cluster randomized controlled trial design, we assigned three of six participating elderly health centres to the experimental group and the other three to the control group. The respondents were 925 (472 in the experimental group and 453 in the control group) elderly health centre attenders aged 65 years or above. They were assessed by MDS-HC and 734 (382 in the experimental group and 352 in the control group) of them were re-assessed one year later. In the experimental group, the medical doctors had been given their patients' profile of potential problem areas identified by MDS-HC before they treated their patients whereas in the control, the medical doctors treated their patients with their usual practice. We found that older attenders in the experimental group improved more than the ones in the control group in only two out of 13 areas. Surprisingly, the patients in the experimental group deteriorated even more than the ones in the control group in terms of bowel incontinence. Our results indicated that the function of the MDS-HC in case finding or screening is limited in the Hong Kong primary medical care setting.