The aim of this study was to validate the nighttime symptoms score (NSS), which incorporates individual scores for difficulty going to sleep and nighttime awakening caused by nasal symptoms and nasal congestion on awakening, as a clinically relevant measure of allergic rhinitis (AR). Fifty-five general season AR (SAR) symptom items were generated by interviews with 14 patients with symptomatic SAR without concomitant asthma for use in an Importance Rating Questionnaire (IRQ). A second group of patients (n = 83) with symptomatic AR without asthma rated the importance of each item on the IRQ. Correlation coefficients were calculated to examine the relationships between the six sleep quality questions on the IRQ and the other AR symptoms and between the symptom questions of the NSS, the Daytime Nasal Symptoms Score (DNSS), and the individual domains of the Rhinoconjunctivitis Quality-of-Life Questionnaire (RQLQ). The majority (94%) of patients with active AR reported some degree of symptoms relating to sleep quality. The six sleep quality items on the IRQ were selected by 71-84% of patients. The sleep quality items were more highly correlated with each other (r = 0.48-0.85) than with the four items of the DNSS (r = 0.01-0.42). There was a moderate-to-strong correlation of the RQLQ sleep domain with the two sleep questions of the NSS (r = 0.44-0.57). The individual symptom questions of the NSS and the DNSS were only moderately correlated with each other. Sleep quality questions measure aspects of SAR that are not captured by daytime SAR symptoms. The results show that the NSS is a valid and relevant clinical measure of the impact of nighttime sleep disturbance on AR patients.