OBJECTIVE: The aim of this study was to compare the costs and clinical consequences of olopatadine, a NCE with a dual mechanism of action (anti-histamine and mast cell stabilizer) with topical levocabastine for the treatment of seasonal allergic conjunctivitis (SAC) in Belgium, France, Germany, Netherlands, Norway, Portugal and Sweden. METHODS: A randomized, controlled, double-masked, multi-country clinical trial compared the efficacy and safety of olopatidine 0.1% bid and levocabastine 0.05% qid. An economic comparison of first-line treatment failures with olopatadine versus levocabastine was modeled using clinical trial results and a standard cost approach. A societal perspective was adopted. Indirect resource utilization was estimated from the clinical trial. Cost of failure was established from Pinto. RESULTS: 210 patients (101 olopatadine, 109 levocabastine) with SAC were treated over 42 days. At day 42, olopatadine-treated patients had a lower redness score (P <0.05) while the difference in itching scores was close to statistical significance (P = 0.062). The first-line treatment-failure rate was 15.8% less (P <0.01) in olopatadine-treated patients. Olopatadine patients had a 1.47 greater chance (P <0.0001) of having a day without symptoms. Olopatadine was well tolerated. Time lost due to SAC was lower than 1 hour on average. Cost of failure varied across countries from 48 € to 72 €. Savings per episode due to first-line failures avoided with olopatadine were 8.84 € in Belgium, 10.97 € in France, 10.94 € in Germany, 7.74 € in NL, 7.61 € in Norway, 10.65 € in Portugal and 11.33 € in Sweden. Sensitivity analyses confirmed the robustness of our findings. CONCLUSION: Based on results of a randomized clinical trial, and resources and costs associated with failure estimated from the literature, our model found that olopatadine is a cost-saving alternative to levocabastine that provides more clinical benefits to patients. Results were consistent over all study countries.