Abstract
All subgroups of the magnetic axial point groups are derived, and the invariant ones are indicated. These subgroups can be used in the determination of the symmetry of the low-temperature phase in phase transitions of crystals that are highly anisotropic in one direction (the ferroelectric transition of the chain-type crystal SbSI at 295K is considered as an example) and of quasi one-dimensional systems (where the order of the principal rotational axis may be any integer).