Objectives: To investigate the effects of Ramdan fasting on plasma levels of ACTH and cortisol in athletic students living in the Jordan Valley (JV) and compare them to those living at above sea level in Ramtha City (RC). Methods: Sample collection and measurements were done in November 1998 from non-fasting and in December 1998 from fasting people. Results: ACTH levels in non-fasting subjects in the JV were 36 ± 4 IU/ml compared to 43 ± 3 IU/ml for those in RC. Cortisol levels were 483 ± 76 (JV) and 539 ± 89 nmol/l (RC). Fasting led to an increase in ACTH (49 ± 6 (JV) and 58 ± 5 IU/ml (RC)) and cortisol levels (637 ± 101 (JV) and 805 ± 72 nmol/l (RC)). Conclusion: Fasting increases ACTH and cortisol levels in an altitude-independent fashion.