Over more than 20 years, Young Lives has followed two cohorts born seven years apart (Favara et al. 2021). This technical note documents the attrition rates from the seventh round of the Young Lives survey carried out in Ethiopia, India (the states of Andhra Pradesh and Telangana) and Peru in 2023–24, when the Younger Cohort were aged 22 and the Older Cohort were 29. It also provides details on the completion rates observed for specific components of Round 7 that required additional informed consent (a self-administered questionnaire, anthropometric measures, reading comprehension, computerised cognitive tasks, and hair samples). In the note, sample attrition is defined as the percentage of participants who could not be located, migrated abroad, have passed away, or have refused to take part in previous rounds, compared to the original sample surveyed in Round 1. Twenty-one years since the Young Lives study began, an average of 81.0% of the original participants remain part of the study across all three countries, with attrition rates of 25.6% in Ethiopia, 11.5% in India and 19.8% in Peru.