Purpose: This study was designed to detect any altitude related changes in colour discrimination of climbers and to possibly use this test to detect acute mountain sickness (AMS) in its prodromal period. Material and Methods: Farnsworth-Munsell 100-Hue (FM-100 Hue) test was performed at 1640m and also at 4200m above sea level on 16 middle aged climbers (mean age: 34.12±8.7 yrs) during a climb on Mt. Agn. Total and sectorial error scores were compared between these altitudes. Results: The total error score (median±range) was 80 (16-277) at 1640m and 104 (36-216) at 4200m (p= 0.905). However, there was no statistically significant difference between this observed detoriation on FM-100 Hue test scores. Conclusion: Research on the effects of various day light conditions and longer acclimatization in larger groups of climbers from various age groups could make early-monitoring of the prodromal signs of emerging acute mountain sickness possible.