The energies and wave functions of stationary many-body states are ana
lyzed to look for the signatures of quantum chaos. Realistic shell mod
el calculations are performed in the JT-scheme for 12 particles in the
sd-shell. Local level statistics are in perfect agreement with the GO
E predictions whereas the eigenvectors show evidence for non-complete
energy dependent chaoticity. The information entropy of individual eig
envectors turns out to be a convenient measure of degree of complexity
of individual wave functions, We discuss the representation dependenc
e and the sensitivity to the interaction strength. The exceptional rol
e of the mean field basis is stressed.