Associations between chronic conditions and work performance (absenteeism, presenteeism, and critical incidents) were studied in reservation agents, customer service representatives, executives, and railroad engineers. Conditions and work performance were assessed with the World Health Organization's Health and Work Performance Questionnaire. Analysis of covariance was used to estimate associations. More work performance was lost from presenteeism than absenteeism. However, chronic conditions more consistently had negative impacts on absenteeism than presenteeism. Conditions with significant effects included arthritis, asthma, chronic obstructive pulmonary disease-emphysema, depression, and chronic headaches. Arthritis had the largest aggregate effect on absenteeism-presenteeism. Only depression affected both absenteeism-presenteeism and critical incidents. Some chronic conditions have substantial workplace effects. Disease management programs for these conditions might have a positive return on investment (ROI). Health and productivity tracking surveys are needed to evaluate ROI and provide quality assurance.