Cough flows and pressures were measured during cough augmentation in healthy subjects and patients with bulbar and nonbulbar amyotrophic lateral sclerosis. Manual assistance increased flow 11% in bulbar (p < 0.01) and 13% in nonbulbar (p < 0.001) patients. Mechanical insufflation-exsufflation increased flow 17% in healthy subjects (p < 0.05), 26% (p < 0.001) in bulbar, and 28% (p < 0.001) in nonbulbar patients. The greatest improvements were in patients with the weakest coughs. Patient group and level of weakness influenced the effect of augmentation.