Many studies report poor compliance with diaries of peak flow. Aim: To determine factors associated with compliance by children. Methods: In 1997,166 children (8-12 years) with recent wheeze, from Wagga Wagga and Moree were enrolled to keep a daily record of peak flow and symptoms for one year. At the end of the follow-up, children and parents completed questionnaires about the study. Compilers were children who submitted more than 6 months of data. Results: 15 (9%) children did not submit any data. 95 (58%) children submitted more than 6 months of data. More parents of compliers (93%) answered the questionnaire than parents of non compilers (66%) (p<0.001) Factor Non Compliers P value compliers Exposed to environmental tobacco 44.8 18.1 <0.001 smoke at home (32.6-57.4) (10.9-27.4 Child had more than 12 episodes of 27.1 28.1 0.89 wheeze in last 12 months (17.2-39.1) (19.4-38.2) Child understood purpose of study 17.5 36.7 0.01 (8.7-29.9) (26.8-47.5) Child had most difficulty completing 25.0 52.0 0.007 diary during holidays (12.1-42.2) (40.1-63.7) Parents considered encouragement 90.2 75.3 0.05 by researchers important (76.9-97.3) (65.0-83.8) Conclusions: The results suggest that asthma severity is not an important factor determining compliance, whereas socio-economic factors, education of the child about the purpose of the study and contact by researchers may be.