We performed a survey concerning prescriptions in the elderly to investigate the influence of ageing on compliance and the occurrence of adverse drug reactions. First, we surveyed 222 outpatients attending at our department (average 70.2 y.o.). The physicians in change examined the account of remaining medicines, and we analyzed the relationship between the compliance with prescriptions, age, diseases and medicines. Secondly, we surveyed 282 inpatients (average 68.0 y.o.). We compared the number of prescriptions before hospitalization, at discharge and 6 months after discharge. We also examined the frequency of adverse drug reactions. The number of medicines, which were prescribed for both in- and outpatients, increased according to age. However, no ageing effect on the number of prescriptions per disease was found. The average number of prescriptions per patient at discharge significantly increased compared to that before hospitalization. The average number of prescriptions of the elderly (above 65 y.o.) admitted at emergency case was significantly more than regularly admitted elderly (p < 0.01). The rate of proper medication taking was significantly higher in the elderly than in the young (p < 0.05). The total percentage of adverse drug reactions among inpatients was 18.8%. Among the patients aged above 60 y.o., the frequency of adverse drug reactions increased according to age. Increased number of the prescribed medicines might be involved in the cause of increased adverse drug reactions in the elderly.