Objective.—To measure the incidence of acute mountain sickness (AMS) in adolescents travelling to moderately high altitudes.

Methods.—The study was carried out on a cohort of 63 adolescents with an average age of 15.9 years during an 8-day trip to Morocco, travelling to altitudes between 3106 m and 4167 m. The incidence of AMS was calculated using the Lake Louise questionnaire, which was completed twice daily by each participant. An episode of AMS was defined as being a score of 3 or more on the Lake Louise questionnaire in the presence of a headache. Difference in incidence between boys and girls was analyzed using 2-tailed Mann-Whitney U testing.

Results.—The daily incidence of AMS among 52 participants with complete data was found to be between 3.8% and 42.3% and increased with increasing altitude. Girls had a statistically significant higher incidence of AMS (80%) compared with boys (55%) (P < .01).

Conclusions.—Acute mountain sickness may occur more commonly in female adolescents than in male adolescents. Overall, however, it appears that the incidence of AMS in adolescents is similar to that found in adults in previous studies.