In Germany, conducting a research project followed by writing a thesis is necessary to receive the title "Doctor" but is not necessary to work as a physician. To determine the reasons that students abandon their dissertations, we conducted and analyzed a survey among 160 fifth and sixth-year medical students at the University of Wuerzburg. Fifteen of 160 respondents (9%) reported to have stopped working on their original project before starting their current replacement thesis research project. Among these 15, the major reasons for abandoning the original research project were: seven (47%) reported lack of supervision, three (20%) reported no recognizable progress, and another three (20%) reported an unacceptable burden of work. Unfamiliarity with experimental methods led two students (13%) to stop working on their original research project. Close supervision and a thorough training remain necessary to prevent students from abandoning medical dissertations and thus should be an essential part of every research project in which medical students are involved.