This talk will introduce the audience to the class of problems that digital circuits are faced with in challenging radiation environments. Such environments include satellites in space, the electronics inside particle accelerators and also a variety of medical applications. After giving an overview of the various effects that may cause malfunctions, different techniques for detection and mitigation of such effects are presented. Some of these techniques concern the transistor-level design of digital circuits, others include triple modular redundancy (TMR) and correction codes. Some open source software solutions that aid in the design and verification of circuits hardened against such problems are presented, and of course a 'lessons learned' from our experiences in the field of particle detector electronics will be shared.