  The most precise measurements are done at present by timing of radiopulsars
in binary systems with two neutron stars. The timing measurements of the
Taylor-Hulse pulsar B1913+16 gave the most precise results on testing of
general relativity (GR), finding implicit proof of existence of gravitational
waves. We show that available results of existing measurements, obtained to the
year 1993, in combination with the results of the Mariner 10 in (1992), give
the boundaries for the variation of the gravitational constant ${\dot G}/{G}$
inside the limits $(-0.6 \div +2)\cdot 10^{-12}$ year{$^{-1}$}.
