[en] In the framework of linearized equations of ferrohydrodynamics, one derives the dispersion equation of the problem on capillary instability of a stationary ferrofluid thread immersed in another ferrofluid of equal density and viscosity. The analytical formulae for the growth rate of a sinusoidal perturbation of a circular cylinder-shaped interface are founded in the limiting cases of large and small Ohnesorge numbers Oh. Numerical calculations carried out under condition Oh>>1 provide insights into the effect of the magnetic force on the capillary break-up of the ferrofluid thread surrounded by a nonmagnetic liquid as well as on the break-up of the nonmagnetic liquid thread being inside the ferrofluid body