Objective - To evaluate the use of a modified whole body plethysmograph in awake sheep. Animals - 10 healthy adult sheep. Procedure - Concurrent measurements of specific airway resistance (sRaw) and pulmonary resistance (RL) were obtained using a novel noninvasive headout constant-volume plethysmograph and esophageal balloon-pneumotachography, respectively. All data were collected before and after external resistive loading with 1 and 5.6 cm H2O/L/s. Functional residual capacity (FRC) was measured by helium dilution for computation of airway resistance (Raw) preloading (Raw = sRaw/FRC). Results - The sRaw and RL were closely correlated in 10 adult sheep. Additionally, sRaw and RL accurately reflected the magnitude of added resistance. The mean FRC was 52 mL/kg and used to calculate Raw. At baseline, the values for Raw were significantly correlated with sRaw and RL. Conclusions and Clinical Relevance - Precise measurements of sRaw and Raw at baseline and sRaw after external resistive loading were obtained by use of this novel noninvasive plethysmographic technology. This method should have application to veterinary patients or animals used in research in which noninvasive rapid or serial measurements of sRaw in the conscious state are required.