After observing three cases of severe recurrent exacerbations of asthma in relation to menstruation, we conducted a survey among women with asthma inquiring about the relationship of asthma symptoms to the menstrual cycle. Of 57 women with asthma, 19 (33%) had significant worsening (p = 0.006) of total pulmonary symptom scores during either the premenstrual period, the menstrual period, or both with maximum increase in dyspnea, wheezing, and chest tightness during the premenstrual period (p = 0.002). The other 38 (66%) women noted no such changes in their asthma. Logistic regression analysis comparing women with and without worsening of their asthma around menstruation revealed that the former group reported significantly more severe wheezing in general (p less than 0.05) and also more severe pulmonary symptoms during the premenstrual period (p less than 0.05). Of the women whose asthma was affected by menses, 13 (68%) had been hospitalized for asthma but only 10 (26%) of the women who were unaffected (p = 0.002). Both dysmenorrhea scores and premenstrual syndrome scores correlated significantly with baseline pulmonary symptom scores in the premenstrual asthma group. It appears that asthma morbidity is affected by the menstrual cycle in a subgroup of women with asthma.