diff --git a/geant4/LEMuSR/doc/running_lem.txt b/geant4/LEMuSR/doc/running_lem.txt
new file mode 100644
index 0000000..25e844c
--- /dev/null
+++ b/geant4/LEMuSR/doc/running_lem.txt
@@ -0,0 +1,84 @@
+RUNNING THE LEM SIMULATION - A QUICK HOW-TO
+
+- T. Shiroka, 13.06.2008 -
+
+Note: G4 LEM simulations have been tested with the following versions: 
+      geant4-09-01 and CLHEP.2.0.3.2. To install both programs refer
+      to the file geant_4.9_inst_log.txt located in the directory doc.
+
+
+Preliminary operations
+======================
+
+Except for the g49 command, all these operations are carried out only once:
+
+- Check out locally the directory:
+  afs.psi.ch/project/nemu/svn/lem/trunk/simulation/geant4/LEMuSR
+
+  located at:
+  http://savannah.psi.ch/viewcvs -> nemu/lem
+
+- Make sure the env.sh is somewhere in your path. BEFORE starting to use
+  Geant4, make sure the relevant variables are set by issuing the command:
+   
+  source /usr/local/geant4/4.9.1/env.sh
+  export G4VRMLFILE_VIEWER="vrmlview"  # Optional (only for VRML graphics)
+   
+  Since these commands should be use every time G4 is used, insert an alias
+  in your e.g. .bashrc file (DO NOT leave gaps or insert CR!)
+   
+  alias g49='source /usr/local/geant4/4.9.1/env.sh; export G4VRMLFILE_VIEWER="vrmlview"; echo "On this machine the G4VRMLFILE_VIEWER=$G4VRMLFILE_VIEWER"'
+
+  Each time one can prepare the G4 enviroment by simply typing: g49
+
+
+Running the macro
+=================
+
+The final user SHOULD compile the code only once, at the beginning.
+Then, each time a different macro is used there is NO need to compile.
+
+The information flow during program execution is linear:
+input data (macro) --> executable --> output data (root)
+
+- To run normally (output on screen, root data on file):
+  lem4 1050.mac
+
+- To write output (output on external file, root data on file):
+  lem4 1050.mac > filename.txt
+
+- To run interactively, comment first the macro line
+  "/run/beamOn", then use a slightly modified syntax:
+  lem4 1050.mac idle
+
+Before running the macro, edit carefully all the relevant fields
+by using the numerous existing comments as a guidance.
+Preferably use an editor capable of syntax highlighting (e.g. kate),
+and set it to the "shell script" mode.
+
+For a correctly running program (automatic features, etc.) all macros, 
+as well as the various field maps should be located in the directory run.
+The run number at the end of the macro file name is used to save data 
+automatically in a root file having the SAME name (e.g. lem4_1050.root),
+as the macro, but located under the directory run/data.
+
+The executable can be run even WITHOUT installing G4 (e.g. under Merlin). 
+In this case, however, the user should copy the private run-time bindings 
+(used by the executable) to the host machine. To list them use either:
+
+ldd exe_name, or 
+objdump -p exe_name (more advanced)
+
+
+Analysing simulation output
+===========================
+
+Since most of the G4 output is written in an external root file, any root 
+command, script or executable could be used for analysing data. Some root 
+example files (e.g. for testing TOF, beam cross section, etc.) will be 
+added soon.
+
+
+
+
+