The Life-Patterns project is a panel-cohort longitudinal study following the life trajectories of 1,908 young people who left school in Victoria in 1991. The project attempts to obtain nuanced pictures of young people's lives in three ways: using a reflexive longitudinal study design, with opportunities for participant feedback and influence on future questionnaire design; using a mix of large-numbers surveying with smaller-numbers in-depth interviewing; and by building ongoing relationships with participants through regular feedback reports on the findings and the impact of the research. The paper uses the example of this project to explore the challenge of participatory approaches to large-numbers longitudinal research. (Contains 1 figure and 2 notes.)