Apparatus for performing in-vitro DNP-NMR measurements on a sample comprises magnetic field generating apparatus (1a, 1b) located in a cryostat (2) and surrounding a bore defining respective NMR and DNP working regions (90, 92). A system for performing DNP on a suitably prepared sample in the DNP working region. A system for performing a NMR process on a sample in the NMR working region. A sample positioning mechanism (5) which can be inserted in the bore (3) to bring a sample in turn into each of the working regions. The magnetic field generating apparatus is suitably structured so that the magnetic field in the DNP working region has a homogeneity or profile suitable for performing DNP on the sample and the magnetic field in the NMR working region has a homogeneity or profile suitable for performing a NMR process on the sample.