Objectives:To assess the medications prescribed for elderly inpatients on specific days during hospital admission with a view to detecting areas of irrational prescription.Methods:It was a prospective study of all patients aged 65 years and above admitted to the medical wards of a Nigerian tertiary hospital over a 12-month period. The World Health Organization/International Network of Rational Use of Drugs (WHO/INRUD) drug use indicators were used to assess drug prescriptions on various days of admission.Results:A total of 1513 patient encounters involving 345 patients aged between 65 and 92 years were assessed on hospital days 1, 3, 5, 7, 14, and 28. The average number of medicines per encounter ranged from 6.1 ± 2.5 on hospital day 1 to 7.8 ± 2.4 on hospital day 28. This difference was statistically significant (F = 14.42; P < 0.05). The percentage of encounters with an antibiotic prescribed ranged from 50.4% on hospital day 1 to 62.9% on hospital day 28 while the percentage of encounters with an injection prescribed decreased from 72.8% on hospital day 1 to 50.0% on day 28.Conclusions:This study suggests some degree of irrational prescribing as evident by the high average number of medicine per encounter and the high percentages of encounters with an antibiotic or injection prescribed. However, there is a need to develop standard values for the WHO/INRUD indicators based on the recently published national treatment guidelines for common elderly diseases which will serve as yardsticks to assess elderly inpatients prescriptions using WHO/INRUD core indicators in future studies.