The purpose of this study was to determine whether there are any consistent spirometric or Dsb findings in patients with LV dysfunction characterized by a clinical diagnosis of CHF and an EF less than 40 percent. We performed spirometry and Dsb in 34 patients, and found that EF correlated only with Dsb. When we separated the patients into those with rales and those without, Dsb correlated strongly with EF only in those with rales. There was no correlation with other spirometric values. Mean Dsb percent predicted was significantly lower in patients with rales despite similar mean EF. Only two of 23 patients without rales had a reduced Dsb while only one of 11 with rales had a normal Dsb. We conclude that Dsb is a good predictor of clinically evident heart failure. When rales are absent, Dsb should be normal in patients with LV dysfunction; when present, Dsb will be diminished in proportion to the EF.