Objectives: Previous studies suggest that flight attendants could have a higher risk for endometriosis than women in other occupations. Our objectives were to compare the rate of endometriosis among flight attendants to the rate in a comparison group of teachers, and to investigate occupational risk factors for endometriosis among flight attendants. Method: We included 1780 flight attendants and 240 teachers aged 18-45 at enrollment. Endometriosis diagnosis was selfreported via telephone interview, and records of individual flights were retrieved from airlines to obtain work schedules and assess exposures for flight attendants. Cox regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for associations between exposures and endometriosis, adjusting for body mass index at interview and using age as time scale. Results: Flight attendants were no more likely to report endometriosis than teachers (adjusted OR 1.3, 95% CI 0.7-2.3). Among flight attendants, there were no clear trends between yearly cosmic radiation exposure, hours worked during normal sleeping hours, or ergonomic factors and endometriosis. A greater number of flights per day (adjusted OR 2.0, 95% CI 1.2-3.3 for 3+ versus 1 flights/day, p trend = 0.007) and fewer time zones crossed per flight (adjusted OR 2.0, 95% CI 1.0-3.7 for 0 vs. 2 + time zones/flight, p trend = 0.04) were associated with a higher rate of endometriosis. Conclusions: The rate of endometriosis increased with number of flights and decreased with time zones crossed, which might be surrogates for exposures specific to flying a series of short flights during the workday.