Hello,
You can use the "vop add" command:

<http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/vop.html#add>

Examples:

vop add #1-25 onGrid #0
vop add #1,2,5 onGrid #5 inPlace true
vop add #1,2 boundingGrid false 

Elaine
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Elaine C. Meng, Ph.D. 
UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab
Department of Pharmaceutical Chemistry
University of California, San Francisco

On Nov 29, 2010, at 7:19 AM, Massimiliano MALETTA wrote:

Hello
I would like to know if merging two maps is possible in Chimera.
I have two *mrc map files and I would like to figure out how to get a third file containing the two maps, just summed. I tried the option morph volume, but in fact it is always down weighting one of them respect to the other.
Thank you for the help.