This pilot study was performed jointly by the WHO Action Programme on Essential Drugs, the International Dispensary Association (IDA) in Amsterdam, The Netherlands, and the Ministry of Health in Khartoum, Sudan. The objectives of the study were (1) to compare the potency and quality of some essential drugs after 16 months storage under extreme climatic conditions in Sudan, in comparison with reference samples; and (2) to pretest the stability of some essential drugs selected for a longitudinal study in the Sudan...