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New 21\,cm line observations of NGC~5204 are presented. A new method is discussed to model the severely warped HI plane. Variations of 60$^\circ$ in position angle and 20$^\circ$ in inclination are needed to model this plane. The derived rotation curve extends out to 13\,$\alpha^{-1}$, and the declining part is reached. By combining this rotation curve with an optical (\pf) rotation curve, a very well constrained mass model (best fit) is presented, with \M$/L$ = 1.4\,$\pm$\,0.1\,\mlo, $r_c$ = 2.7\,$\pm$\,0.1\,kpc and $\sigma$ = 44.0\,$\pm$\,0.1\,km\,s$^{-1}$ ($\rho_\z$ = 0.041\,\M$_\odot$\,pc$^{-3}$). The stellar disk, although dynamically more important than the HI, is a minor contributor to the potential. Many characteristics of the mass distribution place NGC~5204, a magellanic spiral, halfway between bright spirals and dwarf galaxies.
