The U.S. investigations onboard included a radiation physics experiment and several biological experiments using rats, quail embryos and plants. As for all Cosmos missions, the principal objective of Cosmos 1129 was to study the effects of space flight on biological systems, with a particular focus on the biomedical problems observed in men and animals during space flight. A concerted effort was made to maximize the science return from the mission. To this end, virtually every organ and tissue from the rat specimens flown was examined by investigators. Space flight effects on bone and muscle were examined in a series of studies on rats. Rats were also used in an attempt to study mammalian reproductive processes in space. A study of avian embryogenesis was carried out for the first time on this mission. Microgravity effects on plants were investigated using carrot tissue. The radiation exposure of the spacecraft and its contents was measured in a radiation dosimetry experiment. Thirty male specific pathogen free rats (Rattus norvegicus) of the Wistar strain were flown onboard and served as experimental subjects for a wide variety of physiological studies. When the experiments began, the rats were about 85 days old and weighed 300 grams on average. The flight rats were divided into five groups for experimental purposes. They were sacrificed seven to 11 hours after landing (group 1), 32 to 37 hours after landing (group 5), six days postflight (groups 2 and 3), or 29 days postflight (group 4). Seven more Wistar rats were flown as part of the rat embryology experiment. Five of these were females weighing about 340 grams at launch and two were males weighing about 260 grams. Fertilized Japanese quail (Coturnix coturnix) eggs were flown to evaluate the effects of space flight on avian embryological development. The effects of space flight on the rate of cellular metabolism were assessed by studying the growth of crown gall tumors in carrots (Daucus carota). Carrot cell cultures were used to determine if growth and development of plants were affected by space flight.