The respiratory inductive plethysmograph (RIP) is used to measure ventilation from body surface movements. We have compared the accuracy of the two versions of inductance coils used with this instrument. The early version consists of rib cage and abdominal coils sewn into a one-piece jerkin, whereas the new version consists of similar coils attached to two separate bands. Following overnight studies in 12 subjects, we found that less than 50% of separate band RIP tidal volumes were accurate when compared with simultaneously measured spirometric values. The jerkin RIP, however, was accurate in 87% of the breaths measured. Therefore, we advocate the use of the jerkin RIP for prolonged studies because the separate bands appear to move more easily.