Although the U.S. experiment on the Cosmos 1667 mission was meant to be a repeat of the Cosmos 1514 cardiovascular experiment, several improvements were implemented on this mission. Modified post-surgery animal handling procedures minimised the risk of damaging the transducer implants. Data was sampled and recorded more frequently during the inflight period. Two monkeys with flight-type cardiovascular instrumentation were studied in a ground-based Synchronous Control experiment; postflight cardiovascular tests were not conducted after Cosmos 1514. Postural tilt tests were conducted during the pre-flight and post-flight periods in several animals to establish a ground-based pool of normal data for this procedure. This data was compared with the similar body fluid shifts thought to occur in flight. Instrument calibration procedures were modified on this mission to ensure that blood pressure measurements would be accurate. The main objective of U.S. participation in the Cosmos 1667 mission was to measure carotid artery pressure and blood flow during the inflight period. The U.S. provided all flight and ground support instrumentation for this experiment. Raw analogue data from flight and ground control experiments was transferred to the Cardiovascular Research Laboratory at the NASA Ames Research Center for analysis. Hemodynamic data was to be correlated with concurrently recorded Soviet data. A similar correlative study was performed during the Cosmos 1514 mission, where blood flow velocity was compared to total body cardiac output as determined by impedance cardiography. Two rhesus macaques (Macaca mulatta) named Gordyy and Oomka were flown onboard the Biosatellite. Each animal weighed approximately 4 kilograms. Both were instrumented for Soviet neurophysiology studies. The instruments consisted of bilaterally implanted microelectrodes in the vestibular nuclei, and electro-oculogram and electroencephalogram electrodes. Monkeys were housed in Soviet BIOS capsules, as for the Cosmos 1514 mission. U.S. hardware developed for the Cosmos 1514 cardiovascular experiment was used again on this mission. A barometric pressure recorder mounted in the primate capsule was used to correct and normalise the implanted pressure sensor to 760 mm Hg.