In this review, a general introduction to biological oxidants (focusing on reactive oxygen species, ROS) and the biomedical rationale behind the development of materials capable of responding to ROS is provided. The state of the art for preparative aspects and mechanistic responses of the most commonly used macromolecular ROS‐responsive systems, including polysulfides, polyselenides, polythioketals, polyoxalates, and also oligoproline‐ and catechol‐based materials, is subsequently given. The endowment of multiple responsiveness, with specific emphasis on the cases where a molecular logic gate behavior can be obtained, is focused on. Finally, fundamental open issues, which include implications of the “drug”‐like character of ROS‐responsive materials (inherent anti‐inflammatory behavior) and the poor quantitative understanding of ROS roles in biology, are discussed.

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Back Cover: Oxidation‐responsive polymers are predominantly studied in relation to biological oxidants (reactive oxygen species, ROS), most often for therapeutic purposes. In article number https://doi.org/10.1002/marc.201800699, Nicola Tirelli and co‐workers discuss the progress in the field (including cascade and multiple responses), which now allows for finely controlled physico‐chemical mechanisms. Much is now to be learned about the complex roles of ROS in order to precisely understand biological responses.