Magnetic bubble velocities have been measured as a function of applied field gradient in many epitaxial rare earth garret films. The dependence of the velocity on the driving field has been found to show varying degrees of nonlinearity. Also, considerable variations in the mobility and in the degree of nonlinearity have been observed among films of nominally the same composition. At a driving field of 5 Oe across the bubble, velocities ranging from 80 to 2800 cm/sec have been observed. The velocity measurements in these films are discussed in the light of existing theories of domain wall dynamics. The measurements on epitaxial films are compared with mobility measurements made on bulk crystals. In many cases the mobility observed in the epitaxial films has been lower than that expected from the damping parameters measured in the bulk crystals. The possible effects of gallium and aluminum substitutions on the mobility are also discussed. The implications of the occurrence of multiple Bloch‐to‐Néel transitions (Bloch lines) in the wall of magnetic bubbles in epitaxial garnet films on measurements of domain wall mobility are discussed. The presence of these Bloch lines can produce a dramatic reduction of the domain wall velocity, and effects attributable to the dynamic generation of Bloch lines have recently been observed. Different methods of measuring wall mobility are compared in the light of these observations. The influence of temperature, ion implantation and double layer films on wall mobility is also discussed.