We study several mean field dynamo models in disk geometry in an attempt to understand the origin of the nonaxisymmetric magnetic field present in M81. There appear to be three (at least) relevant mechanisms, which are not mutually exclusive. Because field growth times are not very short compared to galactic ages, a predominantly nonaxisymmetric seed field may still give a significantly nonaxisymmetric field after times of order 10 10 yr, even if the stable field configuration is axisymmetric. The spiral structure may give a non-axisymmetric structure to the disk turbulence, and thus to the turbulent coefficients appearing in mean field dynamo theory