A simplified equation was derived by which the uniaxial anisotropyHKof the usual bubble materials can be determined from the field lying in the plane of the sample at which the domains disappear. It was found that a garnet film epitaxially grown on a (111) plane of Gd3Ga5O12shows a sixfold symmetry of the domain erasing field which may be due to the cubic crystalline anisotropy of the sample. This implies that, if the cubic anisotropy cannot be neglected compared to the uniaxial anisotropy, the crystallographic axis in the plane of the film along which the domain erasing field is to be applied should be carefully determined. An estimation was made on the contribution of the cubic anisotropy to the domain erasing field when the field lies along a [110] axis.