  We will present results of studies of several massive stars at different
evolutionary stages, but with similar values of the initial mass: O-supergiants
belonging to association Cyg OB2, unique LBV/post-LBV - Romano's star and two
Wolf-Rayet stars - WR156 and FSZ35. All these stars have similar initial mass
of about 50 Msun. It allows us to consider them a single star at different
moments of life, and it gives an opportunity to track changes in the physical
parameters (such as effective temperature, luminosity, mass loss rate, wind
velocity) and chemical abundances during the life of a massive star. It is
important to test the current evolution theories of such objects.
