EMERGING RESEARCH DEMONSTRATES THAT LOW-DOSE (<0.5 GY) ENVIRONMENTAL AND MEDICAL RADIATION EXPOSURE INCREASES THE RISK OF MORTALITY DUE TO ISCHEMIC CORONARY ARTERY (HEART ATTACK) AND CEREBROVASCULAR (STROKE) DISEASE. RESULTS FROM A RECENT STUDY OF MORTALITY RATES AMONG NON-FLIGHT LOW EARTH ORBIT AND APOLLO LUNAR ASTRONAUTS ALSO SUGGESTS BUT DOES NOT PROVE THAT APOLLO LUNAR ASTRONAUTS HAVE A HIGHER PROPORTIONAL MORTALITY RATE DUE TO CARDIOVASCULAR DISEASE THAN NON-FLIGHT ASTRONAUTS. DESPITE THE POTENTIAL FOR LOW-DOSE RADIATION EXPOSURE TO HAVE SUBSTANTIAL ADVERSE EFFECTS ON THE CARDIOVASCULAR SYSTEM LITTLE RESEARCH HAS BEEN CONDUCTED TO INVESTIGATE THIS PHENOMENON. THIS IS PARTICULARLY URGENT AS GROUPS OF NATIONS AND CORPORATE ENTITIES ARE ACTIVELY PLANNING MANNED MISSIONS BACK INTO DEEP SPACE (I.E. THE MOON AND MARS) WHERE EXPOSURE TO GALACTIC COMIC RADIATION IS PERVASIVE. THE PRESENT PROPOSAL SEEKS TO ADDRESS SOME OF THE FUNDAMENTAL QUESTIONS THAT REMAIN OUTSTANDING INCLUDING: 1) AT WHAT DOSE DOES SIMULATED SPACE RADIATION ADVERSELY AFFECT CARDIAC AND CEREBRAL VASCULAR FUNCTION? 2) DOES SPACE RADIATION AND WEIGHTLESSNESS INTERACT TO PRODUCE GREATER CORONARY AND CEREBRAL VASCULAR DYSFUNCTION THAN EITHER ALONE? 3) DOES SPACE RADIATION AND WEIGHTLESSNESS HAVE DIFFERENTIAL EFFECTS ON CORONARY AND CEREBRAL ARTERIES? 4) IS THE CARDIOVASCULAR DYSFUNCTION INDUCED BY SPACE RADIATION AND WEIGHTLESS SUSTAINED OVER A LONG PERIOD OF RECOVERY POTENTIALLY LEADING TO CHRONIC MORBIDITY AND MORTALITY? 5) DOES DIETARY INTERVENTION (E.G. BLACKBERRY SUPPLEMENT) THAT NORMALLY HAVE POSITIVE IMPACTS ON THE CARDIOVASCULAR SYSTEM SERVE AS EFFECTIVE COUNTERMEASURES FOR RADIATION-INDUCED CARDIOVASCULAR DYSFUNCTION AND IF SO IS IT EFFECTIVE IN BOTH THE CORONARY AND CEREBRAL CIRCULATIONS? 6) IS THE PUTATIVE CARDIOVASCULAR DYSFUNCTION INDUCED BY SPACE RADIATION AND WEIGHTLESSNESS SIMILAR IN MALES AND FEMALES AND IS A DIETARY COUNTERMEASURE EQUALLY EFFECTIVE IN BOTH SEXES? RESULTS FROM THESE STUDIES WILL LEAD TO A GREATER UNDERSTANDING OF THE SUSTAINED CARDIOVASCULAR HEALTH RISKS FOR PROLONGED DEEP SPACE TRAVEL.