BACKGROUND: Data on molecular allergy diagnostics in adults with grass pollen allergy with regard to conjunctival and nasal provocation test outcome and specific immunotherapy is lacking to date. OBJECTIVE: To assess whether molecular allergy diagnostics for grass pollen allergens could help with predicting provocation test outcomes and serve as a basis for future component resolved specific immunotherapy. METHODS: Sera of 101 adults with grass pollen allergy was analysed for IgE against timothy grass pollen (Phleum pratense), rPhl p 1, rPhl p 2, nPhl p 4, rPhl p 5b, rPhl p 6, rPhl p 7, rPhl p 11 and rPhl p12 and correlated to the individuals' outcome in the nasal and conjunctival provocation tests and investigated in regard to a potential component resolved specific immunotherapy. RESULTS: An increasing number of sensitizations to timothy grass allergens was correlated to a positive reaction in the conjunctival (4.9 vs. 3.6, p=0.003) and nasal provocation tests (4.5 vs. 2.2, p=0.0175). In molecular sensitization profiles a substantial heterogeneity was detected, with none of the patients exactly matching the allergen composition of a previously published component resolved specific immunotherapy containing Phl p 1, Phl p 2, Phl p 5a/b and Phl p 6. The results indicate that in 95% of the patients a proportion of 50% of timothy-IgE would be targeted with such a specific immunotherapy, while in 50% and 10% of patients 80% and 90% of timothy-IgE would be targeted respectively. CONCLUSION AND CLINICAL RELEVANCE: Molecular allergy diagnostics is a prerequisite for future component-resolved specific immunotherapy due to the high heterogeneity of sensitization profiles. However, of current clinical relevance is the observed correlation between the number of sensitizations and provocation test outcome.