Hallo, May be this topic has already been discussed, I've not done search, but anyway it seems that PetscBinaryRead from 3.1-p7 doesn't support reading complex double dense matrices. I had to add this code: if (nz == -1) if strcmp(comp,'complex') s = read(fd,2*m*n,'double'); A = reshape(complex(s(1:2:2*m*n),s(2:2:2*m*n)),n,m).'; else s = read(fd,m*n,'double'); A = reshape(s,n,m)'; end else to be able to read them. Regards, Alexander