Evidence as to whether clinician has to give specific treatment in all patients of catamenial hemoptysis is unclear. We considered that the current treatment such as long-term usage of hormonal agent or surgery might be excessive for the catamenial hemoptysis. Therefore, we developed prospective observation study with observation strategy and follow-up for the patients. In sequential four patients of catamenial hemoptysis between December 2000 and November 2001, physical examination, chest X-ray, pelvic ultrasonogram and chest CT scan were taken at both the diagnosis and last follow-up. All patients were only observed without specific treatment within the limit of the possibility and followed for average 58 months. Mean age of patients was 23.5years (range, 22-25years). All patients have a history of undertaking one or two dilatations and curettages before diagnosis. The chest CT scans of all patients presented with ground-glass opacities of peripheral location that were disappeared without any residual lesion at last follow-up. Hemoptysis of two patients was spontaneously disappeared after 6 months. In the other two patients, it was greatly lessened in amount and frequency, then clinically insignificant in one. It was disappeared after subsequent 2 months and then relapsed two times in the late of follow-up of another patient. This study suggests that observation only may be an alternative option in the treatment of catamenial hemoptysis.