Background: It is common that physicians go to work while sick and therefore it is important to understand the reasons behind. Previous research has shown that women and men differ in health and health related behavior. In this study, we examine gender differences among general practitioners who work while sick. Methods: General practitioners (GP's) working in outpatient care in a Swedish city participated in the study (n = 283; women = 63 %; response rate = 41 %). Data were obtained from a large web-based questionnaire about health and organization within primary care. Two questions about sickness presenteeism (going to work while sick) were included; life-long and during the past 12 months, and five questions about reasons. We controlled for general health, work-family conflict and demographic variables. Results: Female physicians reported sickness presenteeism more often than male physicians. Work-family conflict mediated the association between gender and sickness presenteeism. Women reported reasons related with "concern for others" and "workload" more strongly than men. Men reported reasons related with "capacity" and "money" more strongly than women. These differences are likely effects of gender stereotyping and different family-responsibilities. Conclusions: Gender socialization and gender stereotypes may influence work and health-related behavior. Because sickness presenteeism is related with negative effects both on individuals and at organizational levels, it is important that managers of health organizations understand the reasons for this, and how gender roles may influence the prevalence of sickness presenteeism and the reasons that female and male GPs give for their behavior.