Homeopathic coca was tested among high altitude trekkers en route to the Mt. Everest base camp to determine its effect on mountain sickness symptoms. Study participants (n = 24) took homeopathic coca while ascending from 8,000 ft. to 17,600 ft. Measurements included: heart rate, oxygen saturation, and a question naire detailing the occurrence and severity of symptoms. Questionnaire items regarding nausea, headaches, difficulty breathing while asleep all demonstrated statistical significance in the experimental group. Oxygen saturation in the exper imental group was significantly higher. In this placebo-controlled, single-blinded, non-randomized study, homeopathic coca significantly reduced the effects of altitude on trekkers in the experimental group when compared with placebo.