We evaluated birch- and timothy-allergic patients for allergen-specific IgE profiles and health-related quality of life (HRQL). We examined 395 patients with seasonal allergic rhinitis against birch or timothy pollen. Sera were analyzed for IgE reactivity to recombinant allergens (Bet v 1, Bet v 2, Bet v 4; Phl p 1/p 5b, Phl p 7, and Phl p 12) and to native pollen extracts (t3 and g6). Subgroup-specific analyses were performed. Patients with cosensitization against structurally unrelated allergens were termed polysensitized. Patients allergic solely to birch or timothy were labeled monosensitized. HRQL was evaluated using an established questionnaire. In patients polysensitized against native birch pollen (n = 233) the prevalence of allergens was 86% for Bet v 1, 15% for Bet v 2, and 5% for Bet v 4. Similar for timothy (n = 256), the prevalence of allergens was 87% rPhl p 1/p 5b, 5% for rPhl p 7, and 14% for rPhl p 12. Values for birch-monosensitized patients (n = 42) were Bet v 1, 100%, and Bet v 2 and Bet v 4, 0%. Values for timothy-monosensitized patients (n = 35) were Phl p 1/p 5b, 100%; rPhl p 7, 0%; and rPhl p 12, 3%. No difference in HRQL existed between patients sensitized solely against major versus minor allergens in birch-allergic patients. Polysensitized cohorts showed sensitization profiles comparable with published data. Monosensitized patients showed IgE against major allergens in 100% of cases. Patients sensitized solely against major or minor allergens showed no differences in HRQL.