Abstract The high- T c superconductor DyBa 2 Cu 3 O 7− x (SC) and its oxygen deficient tetragonal non-superconducting counterpart (NSC) have been studied by DC magnetisation measurements down to 0.3 K and by 161 Dy Mossbauer spectroscopy down to 0.05 K. The low-temperature Dy 3+ magnetic properties, which are similar in the two compounds, show the influence of crystal fields and Dy-Dy magnetic correlations. The Dy 3+ paramagnetic fluctuation rates also show the influence of these correlations. Magnetic ordering occurs within the Dy sublattices near 1 K. The Dy 3+ saturated magnetic moments show fairly large distributions around mean values of 7.0 (SC) and 7.3 μ B (NSC). These distributions are attributed to crystal field inhomogeneities linked to the sample microstructure. In the SC we compare the average field penetration at the Dy sites with the percentage of the bulk Meissner effect. This suggests that the supercurrents are such that they preferentially shield the rare earth sites.