The sections in this article are 1 Introduction 2 The Electronic Properties of High Spin Cobalt(II) and Nickel(II) Ions 3 Metal Substitution and NMR Parameters 4 Cobalt(II)-Substituted Proteins 5 Nickel(II)-Substituted Proteins 6 Cobalt(II)- and Nickel(II)-Substitution in Magnetically Coupled Dimers 7 Conclusions 8 Biographical Sketches Related Articles