The development of corticosteroids that are delivered directly to the nasal mucosa has alleviated much of the concern about the systemic adverse effects associated with oral corticosteroid therapy. However, given the high potency of these drugs and their widespread use in the treatment of allergic rhinitis, it is important to ensure that intranasal corticosteroids have a favourable benefit-risk ratio. One agent that typifies the systemic safety found in the majority of intranasal corticosteroids is mometasone furoate nasal spray, a potent and effective treatment for seasonal and perennial allergic rhinitis and nasal polyposis. Mometasone furoate does not reach high systemic concentrations or cause clinically significant adverse effects. Results from pharmacokinetic studies in adults and children suggest that systemic exposure to mometasone furoate after intranasal administration is negligible. This is probably because of the inherently low aqueous solubility of mometasone furoate, which allows only a small fraction of the drug to cross the nasal mucosa and enter the bloodstream, and because a large amount of the administered drug is swallowed and undergoes extensive first-pass metabolism. There is no clinical evidence that mometasone furoate nasal spray suppresses the function of the hypothalamus-pituitary-adrenal axis when the drug is administered at clinically relevant doses (100-200 microg/day); consequently, mometasone furoate nasal spray has not been associated with growth inhibition in children. The safety and tolerability of mometasone furoate nasal spray have been rigorously assessed in clinical trials involving approximately 4,500 patients, with epistaxis, headache and pharyngitis being the most common adverse effects associated with treatment in adolescents and adults. The clinical effectiveness of mometasone furoate nasal spray, coupled with its agreeable safety and tolerability profile, confirms its favourable benefit-risk ratio.