On Aug 19, 2008, at 5:36 PM, Thomas Goddard wrote:

  To show a distance between atoms select the two atoms and use menu 
entry Tools / Structure Measurements / Distances and press the Create 
button

You can also select one atom and double click while selecting the other one (i.e. control shift double click) to bring up a popup menu from which you can choose Show Distance.

--Eric

                        Eric Pettersen
                        UCSF Computer Graphics Lab
                        http://www.cgl.ucsf.edu