Prospective cohort studies designs can show how health conditions develop over time. Data linkage enables researchers to join together information from different sources. This case study describes how data collected directly from families of children with cerebral palsy were linked with subsequent hospital admissions data collected from the Health Department over a 5-year period to identify risk factors for respiratory disease in this population. The case gives a behind-the-scenes look at the practicalities of designing and executing a prospective cohort design with data linkage. It discusses designing and piloting a questionnaire, methods of recruitment, timing of data collection, collection and handling of personal details for data linkage, consent for data linkage, and methods for managing and protecting data. It gives a researcher’s eye view of the mechanics of the methods used (including what worked and what didn’t) when tackling problems such as “How do you get an adequate sample size?” “How do you get a representative sample, when you know that some participants will be harder to recruit than others?” “How do you choose your outcome measures?” “Who do you need on your research team?” and “And what can consumers contribute to research?” The case study ends with some practical tips on building and maintaining a research team, supervising research assistants, working with consumers, using strong but memorable passwords, optimizing data accuracy, and what to do if you find you’ve published an error.