BACKGROUND:Use of assisted reproductive technologies (ART) continues to increase, yet little is known of the longer term health of ART conceived offspring. There are some adverse birth outcomes associated with ART conception but the subsequent developmental trajectory is unclear. Undertaking research in this area is challenging due the sensitive nature of the topic and the time elapsed since birth of the ART conceived young adults. The aim of this report is to describe a research protocol, including design and ethical considerations, used to compare the physical and psychosocial health outcomes of ART conceived young adults aged 18-28 years, with their spontaneously conceived peers. DESIGN:This is a retrospective cohort study of mothers who conceived with ART in Victoria, Australia and gave birth to a singleton child between 1982 and 1992. A current address for each mother was located and a letter of invitation to participate in the study was sent by registered mail. Participation involved completing a telephone interview about her young adult offspring's health and development from birth to the present. Mothers were also asked for consent for the researcher to contact their son/daughter to invite them to complete a structured telephone interview about their physical and psychosocial health. A comparison group of women living in Victoria, Australia, who had given birth to a spontaneously conceived singleton child between 1982 and 1992 was recruited from the general population using random digit dialling. Data were collected from them and their young adult offspring in the same way. Regression analyses were used to evaluate relationships between ART exposure and health status, including birth defects, chronic health conditions, hospital admissions, growth and sexual development. Psychosocial wellbeing, parental relationships and educational achievement were also assessed. Factors associated with the age of disclosure of ART conception were explored with the ART group only. DISCUSSION:The conceptualization and development of this large project posed a number of methodological, logistical and ethical challenges which we were able to overcome. The lessons we learnt can assist others who are investigating the long-term health implications for ART conceived offspring.