Hi, I have seen posts regarding this problem before. Here is the log I got after attempting to render a surface representation of the 50S ribosomal subunit (rcsb ID: 3CPW). #0, chain 0: 23S ribosomal rna #0, chain 1: L35E #0, chain 2: 50S ribosomal protein L44E #0, chain 4: 5'-R(*cp*cp*ap*(phe)*(aca))-3' #0, chain 9: 5S ribosomal rna #0, chain A: 50S ribosomal protein L2P #0, chain B: 50S ribosomal protein L3P #0, chain C: 50S ribosomal protein L4P #0, chain D: 50S ribosomal protein L5P #0, chain E: 50S ribosomal protein L6P #0, chain F: 50S ribosomal protein L7AE #0, chain G: HS6 #0, chain H: 50S ribosomal protein L10E #0, chain I: 50S ribosomal protein L13P #0, chain J: HMAL13 #0, chain K: 50S ribosomal protein L15P #0, chain L: 50S ribosomal protein L15E #0, chain M: 50S ribosomal protein LC12 #0, chain N: 50S ribosomal protein L18E #0, chain O: 50S ribosomal protein L19E #0, chain P: 50S ribosomal protein L21E #0, chain Q: HL31 #0, chain R: 50S ribosomal protein L23P #0, chain S: 50S ribosomal protein L24P #0, chain T: 50S ribosomal protein L24E #0, chain U: HL21/HL22 #0, chain V: 50S ribosomal protein L30P #0, chain W: 50S ribosomal protein L31E #0, chain X: 50S ribosomal protein L32E #0, chain Y: HL5 #0, chain Z: 50S ribosomal protein L37E C:\Program Files\Chimera 1.7s\bin\mscalc.exe 1.400000 2.000000 1 MSMSLIB 1.3 started on Local PC Copyright M.F. Sanner (March 2000) Compilation flags C:\Program Files\Chimera 1.7s\bin\mscalc.exe 1.400000 2.000000 0 MSMSLIB 1.3 started on Local PC Copyright M.F. Sanner (March 2000) Compilation flags Surface calculation failed, mscalc returned code 5. Surface calculation frequently fails for large, multi-chain structures. The calculation may be successful if the chains are treated individually, by using the "split" command before generating a surface. If splitting is not desired or the structure is already a single chain, changing molecular surface parameters in the Selection Inspector or (before surface creation) the New Surfaces category of Preferences may allow the calculation to succeed. C:\Program Files\Chimera 1.7s\bin\mscalc.exe 1.400000 2.000000 1 MSMSLIB 1.3 started on Local PC Copyright M.F. Sanner (March 2000) Compilation flags Surface 3CPW.pdb, category ligand, probe radius 1.4, vertex density 2 1 connected surface components Total solvent excluded surface area = 989.35 Total solvent accessible surface area = 1473.85 In this case, I am not interested in splitting the file into its individual chains. I have also unsuccessfully played with the probe-radius and vertex parameters. I should mention that I was able to get this to work with previous versions of Chimera (1.5.something) and that small proteins can be successfully rendered with the latest versions. best, Antón -- Antón Vila-Sanjurjo, PhD Marie Curie fellow Grupo QOSBIOS, Dept. Química Fundamental Facultade de Ciencias Universidade de A Coruña (UDC) Campus Zapateira, s/n 15.071 - A Coruña - España (Spain). tlf: (34) 981-167000 ext:2659 e-mail: antonvila.s@gmail.com