Introduction: Menstrual cycle is an integral part of life in woman and associated with variations in metabolism and endocrine functions. There is widespread agreement about the hormonal changes that occur during the menstrual cycle, but studies on pulmonary functioning during different phases of menstrual cycle are controversial. The purpose of the present study was to evaluate the influence of the normal menstrual cycle on respiratory parameters. Material and methods: Twenty healthy regularly cycling woman (age 20-25 years) kept daily records of lung function parameters during the follicular phase (FP) and luteal phase (LP) over three menstrual cycles. Results: Tidal volume was significantly higher during the LP (0.58±0.01) compared to the FP (0.53±0.01; Mann-Whitney test (U)=4947.50; p=0.0009). Minute ventilation showed the same pattern, being significantly higher during the LP compared with the FP (11.48±0.25 vs 10.24±0.22; U=4558.50; p=0.00004). Forced vital capacity and Index Tiffeneau were higher during the LP phase than that during FP (3.47±0.01 vs 3.41±0.01; U=5092.00; p=0.003 and 86,67±0,89 vs 85,46±1,36; U=4152.50; p=0.04). Peak expiratory flow was significantly higher in LP (6,72±0,08) than in the FP (6.43±0.09; U=5244.00; p=0.006). Breath rate during maximal voluntary ventilation test vas also higher during the LP than that during the FP (52,79±0,87 vs 50,78±0,90; U=5609.50; p=0.044). Forced expiratory volume in one s, forced expired flow from 25-75% of FVC, forced expired flow at 25%, 50%, 75% of FVC and maximal voluntary ventilation were not different between the cycle phases. In conclusion, lung function changes were found during menstrual cycles in healthy women. Conclusion: Increasing the lung function parameters during the luteal phase suggests a possible role for progesterone or other endogenous sex hormones in stimulating the respiratory drive, either centrally or through the peripheral chemoreceptors or by both.