The effectiveness of sharing medical records in improving physician-older patient communication was evaluated in 203 ambulatory chronically ill older patients (mean age, 70.1 years) by a randomized controlled trial. Ninety-five experimental group patients received copies of their physicians' progress notes 1 week after their last office visit, and 108 control patients did not. After 1-2 weeks, knowledge of health problems, medication, and nonmedication treatments was assessed by interview. Experimental group patients knew 74.1% of their health problems, compared with 64.1% in the control groups (P < 0.05). There was no difference in knowledge of medications or adherence to medication regimens. Experimental group patients displayed higher treatment knowledge scores than control group patients (P < 0.01). Less-educated patients showed greater adherence to nonmedication treatments. Shared medical records can enhance physician-older patient communication about health problems and nonmedication treatments, but they do little to enhance medication knowledge or adherence to medication regimens.