Space motion sickness has been estimated as affecting between 1 3 and 1 2 of all space flight participants. NASA has at the moment proposed a combination of promethazine and ephedrine ( P E ) and one of scopolamine and dextroamphetamine ( S D ), both given orally, as well as a transdermally applied scopolamine (TAS), as preventive and ameliorative measures. The reported double-blind study tests the early phase actions and efficacy of the transdermal scopolamine (Transderm ™-V of ALZA Corporation) and compares these in detail to the oral medications. Motion sickness resistance was tested by standardized head movements while accelerating at 0.2°/sec 2 to a maximum rotation of 240°/sec, with an intermediate plateau of 10 min at 180°/sec. To permit weighting motion sickness protection against other system influences, cardiovascular, psychological (subjective and objective), and visual parameter changes were documented for the three therapeutic modes. The relative impact of the various modalities on operational and experimental components of space missions is discussed. A comparison to intramuscularly administered promethazine (a backup therapeutic mode suggested for Space Shuttle use) is also included.