The experimental status of shell structure studies in medium-heavy nuclei f
ar off the line of stability is reviewed. Experimental techniques, signatur
es for shell closure and expectations for future investigations are discuss
ed for the key regions around Ni-48,Ni-56, Sn-100 for proton rich nuclei an
d the neutron-rich N = 20 isotones, Ca, Ni and Sn isotopes. (C) 2001 Elsevi
er Science B.V. All rights reserved.