Partial flow volume curves (PEF25%) were measured daily in eight healthy young adults with experimental rhinovirus colds and in six non-infected controls. There were no differences in the changes in PEF25% values between infected and non-infected volunteers. The co-efficient of variation of the PEF25% in non-infected volunteers was 23%. We conclude that we were unable to detect airway obstruction in volunteers with experimental rhinovirus using the PEF25%, a test with a high co-efficient of variation and, therefore, a low sensitivity for airway obstruction which may be reversed by a deep inhalation. Airway obstruction which was reversed by deep inhalation was not detected in either the infected or uninfected volunteers.