OBJECTIVE This study examined reasons for specialty choice among Swiss residents (post graduate doctors training in specialties). METHODS In 2006, a questionnaire was sent to 8626 Swiss residents registered in postgraduate medical training programmes to obtain specialist qualifications. The response rate was 65% (n = 5631). As residents are allowed to decide on the specialty they want to acquire later in the training process, only residents who had already chosen a specific specialty were included (n = 5038). In responding, residents rated the importance of 19 factors in making their choice of specialty. Categorical principal component analysis was conducted to obtain underlying dimensions within the reasons for choice. A two-way analysis of variance was performed for each dimension to compare the mean object scores for the 10 specialties chosen by the most residents and to examine possible interactions by gender and year of graduation. Contrasts between the specialties were analysed with Scheffe post hoc tests. RESULTS Categorical principal component analyses yielded three factors underlying residents' choice of specialty, which explained 40.8% of the variance in responses: work and time-related aspects; career-related aspects, and patient orientation. Women considered work and time-related aspects and patient orientation to be more important factors in their choice, and career-related aspects to be less important, than did men. Career-related aspects became less important with advancing training status. CONCLUSIONS This study showed that reasons for specialty choice differ according to gender, year of graduation and specialty. With progressing training status, gender differences in reasons for choice and specialty choice may become more pronounced, especially regarding career aspects, which may lead to a change in preferred specialty. Therefore, a modular constructed postgraduate training programme might give residents the flexibility to change from one specialty to another.