The aim of this request is to ask the ALSPAC team to consider including the measurement of sexual orientation (sexual attractions and sexual experiences) in future data collection. Sexual orientation is an important feature of human nature and diversity. While most people identify as heterosexual (attracted to the opposite sex), a substantial number of the population identify as non-heterosexual. This includes lesbian, gay, and bisexual identification as well as a range of emerging sexualities (such as asexual). Scholars from across medicine, behavioural and social sciences have also found that nonheterosexual people are at greater risk of common mental health problems such as depression, anxiety, and suicide compared to heterosexual people. These problems tend to start early in adolescence among nonheterosexual people. It is important to understand the social, psychological, and biological factors that might be involved in contributing to this mental health disparity. This will help researchers to identify the most important risk factors and develop interventions (e.g., psychological interventions) to reduce the burden of these problems on nonheterosexual people. Studies using data from ALSPAC have already helped to identify some of these risk factors and thus continued measurement of sexual orientation in the cohort will prove invaluable to future researchers. In general, future basic and applied scientific research on sexual orientation will provide greater social and cultural understanding of the diversity in human sexuality.