Role-functioning impairment due to medical conditions is a major source of human capital loss and has high economic relevance. From the macroeconomic point of view, population health is an important determinant of workforce productivity and economic development. To achieve sustained growth, Brazil must increase worker productivity, which among other factors depends on the health of the workforce. For employers, rising healthcare costs have a significant impact on business profitability but do they not represent all health-related costs. Several studies show that the total cost of worker health also includes productivity losses and encompasses absenteeism and presenteeism. Numerous international studies have shown the association between health conditions and reduced worker productivity. In Brazil, several studies have shown the relationship between illness and absenteeism, but few have assessed presenteeism. This study describes the association of common medical conditions with absenteeism and presenteeism in a population-based sample of workers in São Paulo Metropolitan Area. Data for this study was from the cross-sectional São Paulo Megacity Mental Health Survey. This included face-to-face interviews conducted on 1,737 employed household residents aged >18 years old. We analyzed data for four non-psychotic mental disorders (mood, anxiety, substance use and impulse-control disorders) using the Composite International Diagnostic Interview (CIDI 3.0) and eight chronic physical conditions with a questionnaire. The presence of physical and mental conditions was determined for the 12 prior month period. The role functioning dimension of the WHO-Disability Assessment Schedule (WHODAS II) was used to assess the number of days in the past month in which respondents were fully or partially able to perform daily activities. Logistic regression analysis was performed to examine the strength of association between these medical conditions and absenteeism and presenteeism. Productivity loss associated with physical and mental conditions is highly prevalent among Brazilian workers. The prevalence of absenteeism was 12.8%. The prevalence of presenteeism was 14.3% for quantitative reduction, 12.9% for quantitative reduction and 13.9% for extreme xiv effort. The mean absenteeism was 1.5 days. The mean work cutback days was 1.4, qualitative reduction 1.4 and extreme effort was 1.7. The physical conditions associated with greater absenteeism included insomnia, diabetes and arthritis. Headache/migraine, chronic pain (neck/back) and digestive disorders were associated with greater presenteeism. The mental disorders associated to greater absenteeism and presenteeism were mood and impulse-control disorders. Headache/migraine and mood disorders were associated with a significantly higher risk of absenteeism, quantitative reduction, qualitative reduction, extreme effort and any day with reduced productivity. Anxiety disorders were associated with absenteeism and any day with reduced productivity. Chronic pain was associated with a signi...