Altitude sickness covers a spectrum of diseases, ranging from the very common altitude headache, to the quite rare but often life-threatening high-altitude cerebral or pulmonary oedema. Diagnosis can be challenging due to subjective reporting of the severity of symptoms, but symptomatology is always considered to be altitude sickness until proven otherwise. Prevention is still the best approach for all forms of altitude sickness, preferably with an appropriate ascent rate rather than pharmacological prophylaxis. Acetazolamide has proven effective in preventing acute mountain sickness in at-risk individuals, but shouldn't be required in all cases. Nifedipine for the prevention of HAPO is indicated only in patients with a history of HAPO or pulmonary hypertension. The first steps to urgently treat altitude sickness are descent and oxygen therapy. Descent isn't always necessary in a hospital setting, but should be a priority in a remote and inaccessible environment. For the treatment of HAPO, descent and nifedipine are the first therapeutic procedures, while dexamethasone with or without acetazolamide is used for the treatment of acute mountain sickness and HACO. Late diagnosis and delayed descent are the most common problems encountered in the field. Although many of the underlying mechanisms of altitude sickness remain unclear, new research in this area may possibly have wider benefits in understanding hypoxia in other clinical settings, as well as improvements in the prevention and management of this rapidly growing clinical problem.