In the development of new MRI pulse sequences and in setting up quantitative diagnostic protocols, benchmarking against a golden standard is a logical step. Several quality assurance (QA) phantoms have been developed. QA phantoms provided by scanner manufacturers mostly contain an aqueous solution, but may be susceptible to motion artefacts that originate from convection currents which do not occur in vivo. Gel phantoms do not exhibit these motion artefacts. Several research groups have developed phantoms that are tuned to specific MRI applications, such as for geometrical precision measurements in stereotactic surgery, T1, T2 and MT mapping, in vivo NMR spectroscopy, magnetic susceptibility mapping, flow measurements, BOLD, and multi-modality imaging. Gel phantoms are also very useful in testing MRI compatibility and safety of medical implants.