Grazax is approved in 27 European countries for treatment of grass pollen-induced hay fever in adults with a proper diagnosis and clinically-relevant symptoms. Grazax is put under the tongue where it dissolves instantly. Treatment should be initiated at least 8-16 weeks prior to the start of the grass pollen season, and similar to traditional immunotherapy the treatment should continue for three years. The recommended dose is one tablet daily. In this review the clinical documentation is briefly discussed. The demonstrated efficacy is clinically relevant and the safety profile is acceptable. Complete documentation of long-term effects is still pending.