On Monday,  5 May 2014 at 19:36, Martin Schöön wrote:
> I have tried to get KOMA and Memoir work in Org-mode. In short: I only get
> error messages telling me they are unknown LaTeX classes.

It would help to know what you have actually tried.

I have the following in my org customisation files:

#+begin_src emacs-lisp
  (add-to-list 'org-latex-classes
               '("komaarticle" "\\documentclass{scrartcl}"
                 ("\\section{%s}" . "\\section*{%s}")
                 ("\\subsection{%s}" . "\\subsection*{%s}")
                 ("\\subsubsection{%s}" . "\\subsubsection*{%s}")
                 ("\\paragraph{%s}" . "\\paragraph*{%s}")
                 ("\\subparagraph{%s}" . "\\subparagraph*{%s}")))
#+end_src

which defines the komaarticle class to use scrartcl from koma.  In the
org file, I then have

#+begin_src org
  ,#+latex_class: komaarticle
#+end_src

HTH,
eric