Previous work has shown decreased lung compliance with high lung wash fluid surface tensions, but normal ratios of lung weight to body weight during stellate ganglion stimulation (SGS) in cats and monkeys. In the present study, effects of SGS on diameters of alveolar ducts were determined in spontaneously breathing cats under ketamine anesthesia. Compliance and pulmonary resistance were also measured. A fluorocarbon cooled to – 100° C was poured onto an exposed lung lobe after rapidly opening the chest after sham operation and during SGS. Examination of the outer 2 mm of the lungs by light microscopy revealed no alveolar-duct constriction by SGS, although compliance decreased by 15 %. Pulmonary resistance was unchanged. Alveolar-duct diameters were 157 ± 4.3 μm (mean ± SEM) in control animals and 163 ± 4.6 μm in SGS cats. Absence of alveolarduct constriction suggests that peripheral airway constriction did not contribute to the decrease in compliance during SGS.