BACKGROUND: Illness as perceived by the allergic patient with asthma and/or rhinoconjunctivitis (RC) can be assessed by measurements of their health-related quality of life (HRQL). For this purpose the RC Quality of Life Questionnaire (RQLQ) has gained general acceptance; however, as most allergic patients experience symptoms from multiple organs, disease-specific HRQL measures may be deficient. This study compares a generic and a disease-specific HRQL instrument in grass and/or mite-allergic patients. METHODS: Two hundred and forty-eight patients with RC and 121 patients with both RC and asthma were studied. Questionnaire information was obtained about allergy-related RQLQ and a generic 15-dimensional instrument for measuring HRQL (15D). Doctors provided general and disease-specific information to classify disease severity according to the global initiative for asthma and allergic rhinitis and its impact on asthma guidelines. RESULTS: Rhinoconjunctivitis patients with persistent moderate-to-severe disease had an impaired quality of life on all items of RQLQ during allergen exposure. The 15D mean score was 0.98 on a day without allergy and 0.83 on a day with allergy (P