Of the 611 people who made the trip, 268 were Germans, with the next highest being the UK at 126. The total number had doubled between 2009 and 2012.
All but four visited the clinic of the best-known assisted dying organisation, Dignitas.
The study, published online in the Journal of Medical Ethics, showed that the average age of patients travelling to Switzerland for assisted dying was 69. Actual ages ranged from 23 to 97.
Almost 60 percent of the patients were women.
German politicians have been wrestling with the euthanasia question for many years. The law currently forbids “killing on demand”.
But medical personnel or other helpers do not risk prosecution for assisting suicide, for example by providing the means for a patient to take their own life.
Chancellor Angela Merkel, who favours stricter regulation of euthanasia, blocked a bill in the last parliament which would have brought associations offering the latter type of help out of their legal grey area.
Health Minister Hermann Gröhe is expected to introduce a bill including stricter regulation of assisted dying once parliament returns from its summer break.
But other members of Merkel's CDU party, such as Bundestag Vice-President Peter Hintze, have argued that the law can't continue to deny the reality of increasing numbers of people seeking out such treatment abroad.
Ethical questions like this are typically left up to individual MPs' conscience when it comes to a vote in the Bundestag. Opponents and supporters of a tougher law are likely to build alliances across party lines in the coming months.