  In this note we show that the latest determinations of the residual Mercury's
perihelion advance, obtained by accounting for almost all known Newtonian and
post-Newtonian orbital effects, yields only very broad constraints on the
cosmological constant. Indeed, from \delta\dot\omega=-0.0036 + - 0.0050
arcseconds per century one gets -2 10^-34 km^-2 < Lambda < 4 10^-35 km^-2. The
currently accepted value for Lambda, obtained from many independent
cosmological and large-scale measurements, amounts to almost 10^-46 km^-2.
