We measured tracheal flow from tracheal sounds to estimate tidal volume(V_T), minute ventilation(V'_I), respiratory frequency(f_B), mean inspiratory flow(V_T/T_I) and duty cycle(T_I/T_TOT). In 11 normals, 3 patients with unstable airways obstruction(UAO) and 3 stable asthmatics(SA) we measured tracheal sounds and flow twice, the first, to derive flow/sound and the second for flow/volume(Ve) relationships from the sound signal. Ve was compared to pneumotach-derived volume (Vm). When seated, facing forward and with neck rotation, flexion and standing, Ve was within 15% of Vm. The error increased with neck extension and supine. We then measured ventilation without mouthpiece or noseclip from tracheal sounds during quiet breathing for up to 30 minutes. Normal results±1SD revealed V_T=0.37±0.065L, f_B=19.3±3.5/min, V'I=6.9±1.2L/min, V_T/T_I=0.31±0.06L/sec, and T_I/T_TOT=0.37±0.04. UOA had large V'I due to increased V_T/T_I. With the exception of T_I/T_TOT, variations in ventilatory parameters were closer to log normal than normal distributions and tended to be greater in patients. We conclude that phonospirometry measures ventilation reasonably accurately without mouthpiece, noseclip or rigid postural constraints.