Rales, peripheral edema and retinal hemorrhage have been reported in sojourners at high altitudes. The purpose of this study was to determine their incidences and their associations with acute mountain sickness. Two hundred trekkers were studied at an altitude of 4,243 m in the Himalayas on the trail to Mount Everest. The subjects either flew to an altitude of 2,800 m and then proceeded on foot (four to six days) or walked in from Kathmandu at 1,300 m (14 to 18 days), all arriving at 4,243 m on foot. They were examined during ascent to an altitude of 5,545 m and again during descent. The age of the population (mean ± 1 standard deviation (SD)) was 33 ± 12 years, and 70 per cent were male. The incidence of acute mountain sickness was 49 per cent in those flying to an altitude of 2,800 m and 31 per cent in those walking to the same altitude (P < 0.001). Rales were found in 23 per cent and were associated (P < 0.05) with acute mountain sickness, peripheral edema and retinal hemorrhage. Peripheral edema occurred in 18 per cent of the subjects and retinal hemorrhages in 4 per cent. Both conditions were associated with acute mountain sickness (P < 0.05) and were more common in women (P < 0.01). We conclude that rales and peripheral edema are common in high-altitude visitors at 4,243 m and that, together with retinal hemorrhage, they are associated with acute mountain sickness.