The antibody-drug conjugate field has made significant progress recently owing to careful optimization of several parameters, including mAb specificity, drug potency, linker technology, and the stoichiometry and placement of conjugated drugs. The underlying reason for this has been obtained in pre-clinical biodistribution and pharmacokinetics studies showing that targeted delivery leads to high intratumoral free drug concentrations, while non-target tissues are largely spared from chemotherapeutic exposure. Recent developments in the field have led to an increase in the number of ADCs being tested clinically, with 3 in late stage clinical trials: brentuximab vedotin (also referred to as SGN-35) for Hodgkin lymphoma; Trastuzumab-DM1 for breast cancer; and Inotuzumab ozogamicin for non-Hodgkin lymphoma. This review highlights the recent pre-clinical and clinical advances that have been made.