 This placebo-controlled clinical trial is designed to evaluate the safety and efficacy of Ragweed MATAMPL as determined by patient symptomatic response to pollen and patient quality of life in an environmental exposure chamber EEC that reproduces the clinical setting. The development of the EEC, which delivers a controlled pollen challenge over time and allows evaluation of a patients response at any time point throughout the challenge process, provides the opportunity to examine various aspects of efficacy of anti-allergic treatments within a single center at various times of the year. The EEC affords a more controlled environment than natural pollen exposure in which variables such as unpredictable pollen levels, varying weather conditions during the study period, and varying levels of pollen exposure within the patient population are eliminated. Furthermore, the question of patient compliance is largely eliminated because the patients are scrutinized closely while they are recording symptoms. In addition, an EEC study is an acceptable study model for determining the dose response for an allergic rhinitis drug as outlined in the draft U.S. Food and Drug Administration FDA guidelines Allergic Rhinitis Clinical Development Programs for Drug Products, April 2000. 