BackgroundParents’ perceived informal social control, defined as the informal ways residents intervene to create a safe and orderly neighbourhood environment, may influence young children’s physical activity (PA) in the neighbourhood. This study aimed to develop and test the reliability of a scale of PA-related informal social control relevant to Chinese parents/caregivers of pre-schoolers (children aged 3 to 5 years) living in Hong Kong.MethodsNominal Group Technique (NGT), a structured, multi-step brainstorming technique, was conducted with two groups of caregivers (mainly parents; n = 11) of Hong Kong pre-schoolers in June 2011. Items collected in the NGT sessions and those generated by a panel of experts were used to compile a list of items (n = 22) for a preliminary version of a questionnaire of informal social control. The newly-developed scale was tested with 20 Chinese-speaking parents/caregivers using cognitive interviews (August 2011). The modified scale, including all 22 original items of which a few were slightly reworded, was subsequently administered on two occasions, a week apart, to 61 Chinese parents/caregivers of Hong Kong pre-schoolers in early 2012. The test-retest reliability and internal consistency of the items and scale were examined using intraclass correlation coefficients (ICC), paired t-tests, relative percentages of shifts in responses to items, and Cronbach’s α coefficient.ResultsThirteen items generated by parents/caregivers and nine items generated by the panel of experts (total 22 items) were included in a first working version of the scale and classified into three subscales: “Personal involvement and general informal supervision”, “Civic engagement for the creation of a better neighbourhood environment” and “Educating and assisting neighbourhood children”. Twenty out of 22 items showed moderate to excellent test-test reliability (ICC range: 0.40-0.81). All three subscales of informal social control showed acceptable levels of internal consistency (Cronbach's α >0.70).ConclusionsA reliable scale examining PA-related informal social control relevant to Chinese parents/caregivers of pre-schoolers living in Hong Kong was developed. Further studies should examine the factorial validity of the scale, its associations with Chinese children’s PA and its appropriateness for other populations of parents of young children.