Infant pulmonary function tests (PFTs) have proven increasingly popular and useful for clinical and research purposes. Informed consent requires accurate information on side effects. Our aim was to quantify minor side effects from a parental point of view by means of a questionnaire. The parents of 97 infants attending for PFTs were asked to complete a simple questionnaire. Eighty-one parents (84%) returned the questionnaire. Forty-one percent felt that their infants were not troubled by the process of administering the sedative chloral hydrate, whereas 55% suffered mild to moderate distress. In contrast, 94% of infants were not distressed by the actual PFTs. Similarly, 46% of parents were not distressed by the administration of sedative to their infant, with 49% expressing distress to a mild or moderate degree. Although 73% of parents were not distressed by watching their infants undergo the PFTs, 27% were to a mild to moderate degree. Seventy-three percent of infants were untroubled on waking. Seventy percent of infants had a good nights sleep after the PFTs. The vast majority of parents (94%) were happy to recommend that others allow their infants to undergo similar testing. We noted that most problems caused by infant PFTs relate to the administration of the sedative. Most infants awake from the tests not distressed and sleep normally the following night.