Every year, thousands of outdoor trekkers worldwide visit high-altitude (>2500 m) destinations. Although high-altitude areas per se do not harbor any specific agents, it is important to know the pathogens encountered in the mountains to be better able to help the ill sojourner at high altitude. These are the same pathogens prevalent in the surrounding lowlands, but various factors such as immunomodulation, hypoxia, physiological adaptation, and harsh environmental stressors at high altitude may enhance susceptibility to these pathogens. Against this background, various gastrointestinal, respiratory, dermatological, neurological, and other infections encountered at high altitude are discussed. Because there are few published data on infections at high altitude, this review is largely anecdotal and based on personal experience.