The space adaptation syndrome SAS, is an operationally relevant biomedical problem for manned space flight. In an effort to develop better methods for the prediction, prevention, and treatment of SAS, investigators at the NASA-Johnson Space Center have initiated a systematic, long range program of operationally oriented data collection on all individuals flying Space Shuttle missions. Preflight activities include the use of a motion experience questionnaire, laboratory tests of susceptibility to motion sickness induced by Coriolis stimuli and determinations of anti-motion sickness drug efficacy and side effects. During flight, each crewmember is required to provide a daily report of symptom status, use of medications, and other vestibular related sensations. Additional data are obtained postflight. During the first nine Shuttle missions, the reported incidence of SAS has been 48. A wide range in severity of symptoms has been reported with general malaise, anorexia, nausea, and emesis being the most frequently described. As in the past, self-induced head motions and unusual visual orientation attitudes appear to be the principal triggering stimuli. Anti-motion sickness medication, although used by a high percentage of crewmembers, has been of limited therapeutic value.