The delivery of genes and drugs remains an active research area, with new challenges arising from the need to deliver specialized cargo, including antibodies, peptides, proteins and oligonucleotides and the need of reaching desired release profiles. Polymer-based systems hold great promise, as polymers can be designed and modified to meet new challenges. Frontline investigators describe polymer systems, such as polyethylenimine, stimuli-responsive hydrogels, and metal-organic nanomaterials, to deliver specific therapeutics, such as genetic materials and anticancer drugs, in controlled manners. Polymer chemists, pharmaceutical scientists, material chemists, and other researchers will find this collection valuable for their research.