I am trying to work with a data set that has three copies of a protein complex per asymetric unit in the cell. It is a rather large complex. I can delete two of the copies and work with only one complex. There are 9 chains in each complex. 3 oligonucleotide sequences, and 6 proteins of different sizes, the largest having about 1400 residues. The way in which I selected only one complex to visualize was to delete the other 18 chains one at a time. There must be a way of deleting each of the other two copies all at once but I did not try to find it in the Chimera tutorial list. The deletion only eliminates the image of each complex. Both complexes are still there in the total data set. The result is that saving a session takes about three minutes because it saving all the coordinates of the three copies of the complex. How can I make the process more efficient and delete two copies from the coordinate data set. Thank you Arthur G. Szabo