Introduction: The concepts of 'sex' and 'gender' are both of vital importance in medicine and health sciences. However, the meaning of these concepts has seldom been discussed in the medical literature. The aim of this study was to explore what the concepts of 'sex' and 'gender' meant for gender researchers based in a medical faculty. Methods: Sixteen researchers took part in focus group discussions. The analysis was performed in several steps. The participating researchers read the text and discussed ideas for analysis in national and international workshops. The data were analysed using qualitative content analysis. The authors performed independent preliminary analyses, which were further developed and intensively discussed between the authors. Results: The analysis of meanings of the concepts of 'sex' and 'gender' for gender researchers based in a medical faculty resulted in three categories; "Sex as more than biology", with the subcategories 'sex' is not simply biological, 'sex' as classification, and 'sex' as fluid and changeable; "Gender as a multiplicity of power-related constructions", with the subcategories: 'gender' as constructions, 'gender' power dimensions, and 'gender' as doing femininities and masculinities; "'Sex and gender as interwoven", with the subcategories: 'sex' and 'gender' as inseparable and embodying 'sex' and 'gender'. Conclusions: Gender researchers within medicine pointed out the importance of looking beyond a dichotomous view of the concepts of 'sex' and 'gender'. The perception of the concepts was that 'sex' and 'gender' were intertwined. Further research is needed to explore how 'sex' and 'gender' interact. Minor Correction: Error in Headings and Error in References (2013-06-25)In the Results section, under the sub-heading "Sex as More than Biology", the three following headings should all be sub-headings of "Sex as More than Biology":'Sex' is not simply biological, 'Sex' as Classification, and 'Sex' as Fluid and ChangeableThere is an error in Reference 9. The following is the correct reference:Christianson M, Alex L, Fjellman Wiklund A, Hammarström A, Lundman B (2012) Sex and gender traps and springboards: A focus group study among gender researchers in medicine and health sciences. Health Care for Women International 33: 739-755.