Physicians regard individuals with dysthymia as having relatively normal levels of functioning. This study examines in detail the work impact of dysthymia in a population of employed primary care patients. As part of an observational study conducted between 2001 and 2003 in clinics associated with three health plans in Massachusetts, we compared 69 patients diagnosed with DSM-IV dysthymia without concurrent major depressive disorder to 175 depression-free controls. Patients were employed at least 15 h per week, had no immediate plans to leave the labor market, and no major comorbid medical conditions. We assessed work absences and productivity loss due to on-the-job performance limitations ("presenteeism"). Patients with dysthymia, compared with controls, had less stable work histories and a greater frequency of significant problems at work. While absence rates were not significantly different (1.2 vs. 0.74 days, P<.09), individuals with dysthymia experienced significantly greater on-the-job productivity loss (6.3% vs. 2.8%, P<.0001). Dysthymia is an unrecognized cause of work impairment that has long-term negative consequences for individuals and their employers. The persistence of dysthymia with its serious impact on work functioning calls out for the development of new interventions.