BACKGROUND Reported wheeze is the cornerstone of asthma diagnosis. AIMS To determine what parents understand by wheeze. METHODS Two studies were undertaken: (1) Parents of clinic attendees with reported wheeze (n=160) were asked by questionnaire what they understood by “wheeze” and how they knew their child was wheezy. Responses were compared to definitions of wheeze in 12 epidemiology studies and their response options. (2) The extent of agreement of parents' reports (n=139) of acute wheezing in their children and clinicians' findings of “wheeze” and “asthma” was examined. RESULTS (1) “Sound” and “difficulty in breathing” were perceived central to “wheeze”. “What you hear” was not selected by 23% (95% confidence interval (CI) 16–30%). “Whistling” was mentioned by 11% (CI 6–15%) but featured in 11 of 12 epidemiology questionnaires. (2) There was les than 50% agreement between parents' and clinicians' reports of wheeze and asthma. CONCLUSIONS Conceptual understandings of “wheeze” for parents of children with reported wheeze are different from epidemiology definitions. Parents' reports of acute wheeze and clinicians' findings also differ.