The effect of cetirizine on quality of life (QOL) in subjects with perennial allergic rhinitis (PAR) has been previously evaluated using generic instruments. While generic QOL tools are used across various conditions, disease-specific instruments evaluate the impact of treatment on areas that are affected by that particular condition. This study evaluated the effect of cetirizine on symptom severity and health-related QOL, using a disease-specific instrument, in adults with PAR. This randomized, double-blind, placebo-controlled study was conducted at 15 U.S. centers outside the pollen allergy season. After a 1-week placebo run-in period, qualified subjects aged 18-65 years with PAR were randomized to once-daily cetirizine 10 mg (n = 158) or placebo (n = 163) for 4 weeks. Change from baseline in total symptom severity complex (TSSC) and overall Rhinitis Quality of Life Questionnaire (RQLQ) scores were primary efficacy end points. Cetirizine produced significantly greater improvements in mean TSSC for each treatment week (p < 0.05) and for the entire 4-week treatment period (p = 0.005) compared with placebo. After 4 weeks, cetirizine-treated subjects reported significantly greater overall improvement in RQLQ scores compared with placebo-treated subjects (p = 0.004). After 1 week, cetirizine produced significant improvements in the nasal symptoms, practical problems, and activities RQLQ domain scores compared with placebo (p < 0.05). After 4 weeks, cetirizine-treated subjects reported significant reductions in these RQLQ domain scores and in emotion domain scores compared with placebo-treated subjects (p < 0.05). Cetirizine 10 mg daily produced significant improvements in symptom severity and allergic rhinitis-related QOL compared with placebo in adults with PAR.