Development of imunoassays for haptens like steroids requires conjugation of these apolar and low molecular weight molecules with usually polar and larger proteins molecules for preparation of desired immunogen and enzyme conjugate. Conjugation chemistries employed in preparation of these immunoconjugates to a very large extent define the assay parameters like specificity and sensitivity. This book is aimed at critically examining the role of the spacer or linker arms used in preparation of immunogens and enzyme conjugates in hapten immunoassay, by compairing polarities, chain length, rigidity and fexibilities of these linkers molecules. The book is an attempt to bring together the various aspects of conjugation chemistry and immunoassay devlopment of haptens in general and would be specially useful for proffessionals and researchers in the field of immunodiagnostics and combitorial chemistry.