I did a survey on the demand for complementary medicine among patients of the gynaecologcial department here in Munich. We collected a couple of hundred questionnaires and I am currently writing two different papers: one dealing with our findings concerning the cancer patients and another about the results from our patients in pregnancy and after birth. I finished the first one and I am currently sitting on the second one. I am wondering now: obviously, the introduction and discussion sections are completely different, but my method section is more or less the same. Can I simply use my method section verbatim also for the other paper? The papers will be submitted to two different journals in the end.
Copying entire sections verbatim between two papers is generally considered self-plagiarism and/or dual-publication. It's frowned upon academically, and may trigger additional unwanted review by plagiarism-detection software.
However, some disciplines- particularly those in the medical sciences- have come to accept that duplication of text between Methods sections of different papers such as in your situation is inevitable. Check with your adviser to be sure this is OK in your discipline (and potentially the editors of the journals you are submitting to), but copying the core of the methods section should not be objectionable.
Note that there are some good practices to follow when doing so. At a minimum you should provide a citation in the methods section to each companion paper explaining that this survey had multiple objectives when it was designed. You should also be able to provide some text describing why the described methodology is suitable for addressing the central question of this particular paper, and why the results from each of the companion papers don't affect the results of this particular paper.
Please note that duplication of text across other sections, especially results and data sections, is always considered a major academic offense.