Recent studies have suggested that female flight attendants may experience increased rates of spontaneous abortion. We conducted a survey of female flight attendants who were pregnant at any time between January 1, 1990, and December 31, 1991 (n = 418) using a mailed self-administered interest survey(response rate, 60%) and follow-up questionnaire regarding reproductive outcomes and potential risk factors for adverse outcomes (response rate, 64%). The cumulative hazard of spontaneous abortion was 17% when maternal age, smoking, alcohol use, and prior spontaneous abortions were controlled for, using a Cox life-table regression model. Of the female flight attendants who worked outside the home, 47 of 321 (15%) experienced a spontaneous abortion, compared with 6 of 73 (8%) who did not work outside the home during the pregnancy period (odds ratio [OR] = 1.91, 95% confidence interval [CI] = 0.78-4.66). Flight attendants who experienced a spontaneous abortion during their first pregnancy during the study period reported working significantly more flight hours per month during their pregnancy (74 hours per month) than did flight attendants who delivered a live birth (64 hours per month)(Student's t = -3.30, P = 0.002). We conclude that although the results of this study must be considered preliminary because of the relatively low overall response rate (38%), we did not find an overall increased risk for spontaneous abortion among flight attendants, compared with other working women (10%-20%). Women who continue working as flight attendants during pregnancy and those who work relatively higher numbers of flight hours during pregnancy may, however, be at increased risk for spontaneous abortion, compared with flight attendants who do not perform such work.