Parents and primary caregivers of children with asthma are limited in normal daily activities and experience anxieties and fears due to the child's illness. We have developed the Paediatric Asthma Caregiver's Quality of Life Questionnaire (PACQLQ) to measure these impairments. The objective of this study was to evaluate the measurement properties of the PACQLQ. A 9-week single cohort study was conducted with assessments at 1, 5 and 9 weeks. Participants in the study were primary caregivers of 52 children (age 7-17 years) with symptomatic asthma, recruited from notices in the local media and paediatric asthma clinics. Caregivers completed the PACQLQ, Impact-on-Family Scale and Global Rating of Change Questionnaires. Patients completed the Paediatric Asthma Quality of Life Questionnaire and an asthma control questionnaire. Spirometry and beta-agonist use were recorded. The PACQLQ was able to detect quality of life changes in those caregivers who changed (p < 0.001) and to differentiate these from the caregivers whose quality of life remained stable (p < 0.0001). The PACQLQ is reproducible in subjects who are stable (ICC = 0.84), and showed acceptable levels of longitudinal and cross-sectional correlations with the child's asthma status and health-related quality of life and with other measures of caregiver health-related quality of life. The PACQLQ functions well as both an evaluative and a discriminative instrument.