Employers are becoming concerned with the costs of presenteeism in addition to the healthcare and absenteeism costs that have traditionally been explored. But what is the true impact of health conditions in terms of on-the-job productivity? This article examines the literature to assess the magnitude of presenteeism costs relative to total costs of a variety of health conditions. Searches of MEDLINE, CINAHL and PubMed were conducted in July 2008, with no starting date limitation, using 'presenteeism' or 'work limitations' as keywords. Publications on a variety of health conditions were located and included if they assessed the total healthcare and productivity cost of one or more health conditions. Literature on presenteeism has investigated its link with a large number of health conditions ranging from allergies to irritable bowel syndrome. The cost of presenteeism relative to the total cost varies by condition. In some cases (such as allergies or migraine headaches), the cost of presenteeism is much larger than the direct healthcare cost, while in other cases (such as hypertension or cancer), healthcare is the larger component. Many more studies have examined the impact of pharmaceutical treatment on certain medical conditions and the resulting improvement in on-the-job productivity. Based on the research reviewed here, health conditions are associated with on-the-job productivity losses and presenteeism is a major component of the total employer cost of those conditions, although the exact dollar amount cannot be determined at this time. Interventions, including the appropriate use of pharmaceutical agents, may be helpful in improving the productivity of employees with certain conditions.