OBJECTIVES: To quantify the magnitude of reduced productivity in the workplace related to allergic rhinitis and to identify its significant correlates. METHODS: A diverse population of 14,000 employees affiliated with 10 western U.S. employers were asked to participate in a study of allergic rhinitis. The anonymous, cross-sectional, self-administered questionnaire was distributed at the worksite and returned to a third party to ensure confidentiality. The instrument included items assessing allergy severity/symptomatology, medication use, health service utilization, knowledge and practices, sociodemographics and reduced productivity (due to full and partial missed days and presenteeism). The response rate was 38%, with 2,493 reporting that they currently had eye or nose allergies. RESULTS: During the four week period prior to the survey, allergic respondents reported missing a total of 16.4 hours of work; 1.97, 2.54, and 11.91 hours were due to full days missed, partial missed days, and presenteeism, respectively. On average, for presenteeism, respondents reported working 6 of 20 days when their allergy symptoms were worse than normal, and rated themselves as 75% productive on these days. A stepwise linear regression identified a) symptomatology, b) allergy-related physician visits, c) severity of medication side effects, d) younger age, e) overall rating of allergy severity, f) lower education, g) receipt of allergy shots, and h) low knowledge of allergies as statistically significant predictors (p<.05) of reduced productivity. CONCLUSIONS: Data from this study confirm earlier research findings of the substantial disease burden associated with allergic rhinitis. Extrapolating to a full year, employees with allergic rhinitis could be expected to lose 213 hours of productivity, which at $20/hour wage rate translates into $4,260. Patient knowledge (self-management behaviors) and use of medications with fewer side effects (non-sedating antihistamines) are associated with increased productivity suggesting that various disease management strategies could be highly cost-effective.