The aim of this study was to evaluate the agreement between children and proxies as well as the agreement between methods of administration in assessing Health-Related Quality of Life (HRQoL) using the TNO AZL Children's Quality Of Life (TACQOL) questionnaire. A random sample from a Dutch cohort of 14-year-old very low birth weight children and their parents were invited to participate in a face-to-face (n = 150) or telephone interview (n = 150). Participants were also sent a questionnaire by mail. The response rate was 83%. Inter-rater and intermethod agreement were generally good in observable HRQoL domains, and moderate in less readily observable, and possibly less stable, domains such as moods, pain and physical symptoms, and social functioning. In measuring children's HRQoL using the TACQOL, the results and their interpretation are dependent on the source of information and the method of administration. © 2000 Blackwell Science Ltd.