Nasal congestion is a frequent, bothersome symptom of seasonal allergic rhinitis (SAR). Mometasone furoate nasal spray (MFNS) has established efficacy in treating nasal allergy symptoms, but no study has been conducted with the primary purpose of evaluating MFNS for relief of congestion. This study assessed MFNS for congestion and other nasal symptoms in SAR. Two double-blind, placebo-controlled studies randomized symptomatic SAR patients to 15 days of MFNS, 200 micrograms, or placebo q.d. each morning. Participants scored individual components of total nasal symptom score (TNSS; congestion, rhinorrhea, sneezing, and itching) on a 4-point scale in the morning (A.M.) and evening (P.M.). Symptoms were scored for the time of assessment (NOW) and for the previous 12 hours (PRIOR). The pooled population comprised 684 patients randomized to MFNS (n = 344) or placebo (n = 340). Change from baseline in A.M./P.M. PRIOR nasal congestion score averaged over days 1-15, the primary end point, was significantly (p < 0.001) greater with MFNS than with placebo (0.68-point [25.2%] reduction versus 0.45-point [16.0%] reduction, respectively). Reduction in A.M./P.M. PRIOR TNSS averaged over days 1-15, a key secondary end point, was also superior with MFNS (2.83 points [28.5%] versus 1.79 points [17.6%]; p < 0.001). Predose A.M. NOW congestion, other nasal symptoms, and TNSS improved significantly more with MFNS, indicating 24-hour efficacy. Adverse events were infrequent and localized; the most common (epistaxis and pharyngolaryngeal pain) occurred in 1.0% of MFNS patients. MFNS q.d. provides sustained relief for nasal congestion and other SAR symptoms.