condition show the same relation as masses obtained from photometry and evolution models, which confirms the absence of systematical difference between these evaluations.

[**4. Conclusions**]{}

As it was shown above, if to assume the marginal stability of inner parts of disks of spiral galaxies, one can estimate local values of disk surface densities and as the next step — the absolute and relative values of their total masses or, strictly speaking, the upper limits of masses for stable equilibrium disks. These estimates in most cases appear to be in a good agreement with the values obtained from photometric data on the basis of stellar population evolution models (Fig. 1b, Fig. 5). It allows to admit that the disks of most spiral galaxies are close to the marginally stable state.

Evidently, mass and density estimates presented in this paper for any given galaxy remain rather rough, mainly due to large errors of radial velocity dispersion $c_r$, and, to a lesser degree, of radial scalelength $h$ values. For some of the galaxies the resulting errors exceed a factor of 2 (see Fig. 1). Thus to obtain more reliable estimates for individual galaxies one have to construct dynamical models consisted of several components 