The American Academy of Allergy sponsored a 2-yr "double blind" multicenter study of the effect of Rinkel injection therapy (RIT) compared with a histamine placebo in subjects with atopic rhinitis. Accumulated data included the symptom, medication, and physical examination scores and specific IgE antibody levels measured by the radioallergosorbent test (RAST). A total of 155 subjects (81 treated, 74 placebo) entered the project from six centers during their respective ragweed, grass, and mountain cedar pollen (from one center) seasons for a total of 11 pollen seasons. The total mean cumulative dose of extract was 18.6 PNU, which is much lower than recommended for standard immunotherapy. With one exception, none of the centers reported a consistent significant difference between the pollen extract-treated and placebo-treated groups in any of the weekly mean scores or the RAST before, during, and after the pollen seasons. For 4 wk after the height of the mountain cedar season the group treated with pollen extract showed a significant decrease in weekly mean symptom and medication scores as compared with the placebo group. The overall comparison of the mean seasonal scores for the entire study, however, showed no significant difference between the treated and placebo groups. We conclude the RIT is no more effective than a histamine placebo in influencing the weekly mean symptom, medication, and physical examination scores or IgE antibody levels.