The variation of topological defect density and hexatic order parameter were measured over a range of microTesla fields in a 2-D superconducting vortex glass. This was achieved through scanning SQUID microscopy of the vortex distribution in YBa2Cu3O7−δ thin films under field-cooled conditions. It was discovered that, although the defect density decreased for increasing magnetic fields, giving the impression of a more latticelike vortex distribution, the hexatic order parameter also decreased, showing that the distribution was less orientationally ordered. Abstract-The variation of topological defect density and hexatic order parameter were measured over a range of microTesla fields in a two-dimensional superconducting vortex glass. This was achieved through scanning SQUID microscopy of the vortex distribution in YBa2Cu3O 7−δ thin films under fieldcooled conditions. It was discovered that while the defect density decreased for increasing magnetic fields, giving the impression of a more lattice-like vortex distribution, the hexatic order parameter also decreased, showing that the distribution was less orientationally ordered.