The objective of this analysis was to examine the answering rates, internal reliability and external validity of the Family Affluence Scale (FAS) employing data from the 2002 Irish Health Behaviour in School-aged Children study HBSC; a cross-sectional survey of 8,424 Irish schoolchildren aged 10-18. Father's occupation was reported by 80.6% of the schoolchildren and 60.6% reported on mother's occupation, while over 96% reported on the FAS items. Lower answering rates on parental occupation were found among younger schoolchildren and among those with poorer material circumstances. Analysis of the FAS revealed a moderate internal reliability and FAS scores were significantly associated with reported parental occupation. The traditional SES measures suffer from poor answering rates that pose a serious methodological threat. The FAS has moderate internal reliability and does not capture the SES status in full, but it has high completion rates, and can be used as an additional measure of SES in late childhood and adolescence.