Fourteen patients with cystic fibrosis were trained in 2 self-administered chest physiotherapy (PT) techniques: high-pressure PEP-mask physiotherapy (PEP), and autogenic drainage (AD). They then visited the clinic on 5 consecutive days, and, in a random order, performed 1 of the following: PEP, AD, PEP followed by AD (PEP-AD), AD followed by PEP (AD-PEP), and, no PT except for spontaneous coughing. Lung function was measured repeatedly before, during, and after PT; time needed for and sputum produced by each form of PT was recorded. PEP produced the highest amount of sputum, followed by PEP-AD, AD-PEP, and AD; all 4 forms of PT produced significantly more sputum than coughing. Lung function improved significantly after PEP, AD, and PEP-AD, but PEP-induced changes did not exceed those after AD. Within the investigated group, the PEP-induced lung function improvement per milliliter of sputum produced was significantly lower for those patients with airway hyperreactivity. The fact that the highest sputum yield with PEP was not reflected in higher PEP-effected lung function changes might thus be explained by PEP-induced bronchospasm in patients with airway hyperreactivity. PEP clears more sputum than AD or combined techniques; patients with airway hyperreactivity, however, should either prefer AD or should take a bronchodilator premedication before PEP.