Book excerpt: The avidin-biotin complex has been used for isolation (affinity chromatography), localization (affinity cytochemistry, cell cytometry, and blotting technology), and diagnostics (immunoassay, histopathology, and gene probes). Recently, usage of the system has been extended to include other areas. This volume covers these new applications and methodologies including hybridoma technology, bioaffinity sensors, affinity targeting, and drug delivery, as well as cross-linking, immobilization, and fusogenic studies.