Singlet-state NMR (see Refs. ) offers an exciting possibility to overcome the drawbacks associated with hyperpolarized 1 H imaging . When parahydrogen is added to an unsaturated precursor molecule, the protons remain in a nonmagnetic singlet state, as long as they remain chemically and magnetically equivalent. This state is neither directly observable in MRI, nor can it be manipulated by radiofrequency (rf) pulses. Additionally, the proton singlet state is immune to certain relaxation mechanisms , and can have a much longer lifetime. Thus, the hyperpolarization can be stored in the singlet state until the molecule undergoes a chemical reaction that renders the protons chemically or magnetically inequivalent. This breaks the proton singlet state, and observable hyperpolarized NMR signals are released. These favourable properties of the singlet state open up new possibilities to perform hyperpolarized 1 H MRI by injecting a biomolecule supporting a singlet state with a long nuclear spin lifetime, which is converted in vivo to an NMR-visible substrate. Such an experiment would have the following advantages: 1. Until metabolism of the molecule, the protons relax relatively slowly; 2. The background 1 H NMR signals of water and fat in the body can be suppressed with rf pulse techniques, while the nonmagnetic singlet state remains unaffected ; 3. This experiment relies on the appearance of an NMR signal rather than a peak shift, and so is insensitive to the limited chemical shift dispersion.