The Spacelab Life Sciences missions are intended to support Life Sciences experiments. The Spacelab Life Sciences 1 (SLS-1) mission originated with a call to the scientific community for experiments in 1978. Accepted experiments involved humans, primates, rodents, amphibians, and plants. The original payload configuration has been reduced to include human, passive rodent, and basic biology experiments and engineering evaluations.Human experiments will address effects of micro-gravity on various physiological parameters during and postflight. Investigations with nonhuman subjects will study microgravity effects on the cardiopulmonary, cardiovascular, and musculoskeletal systems, on the regulation of blood volume and erythropoiesis, and on calcium metabolism and gravity receptors.SLS-1 will serve as a stepping stone in establishing capabilities for flying nonhuman subjects and performing in-flight manipulations on these subjects without jeopardizing the crew environment. Fundamental technology incorporated in the animal holding facilities and laboratory work bench will be used in subsequent missions and in the future Space Station.