Continuous distributions of specific tidal ventilation were recovered from nitrogen washouts in 29 patients with cystic fibrosis and 22 normal subjects along with other pulmonary parameters to assess the utility of the recovered distribution in describing the progress of the disease. Normal subjects showed predominantly unimodal distributions of a pattern showing a small amount of ventilation going to units with high specific ventilation. Multimodal distributions were the rule in the cystic population with only subjects with normal pulmonary function having unimodal distributions.