  The detection of some tiny gravitomagnetic effects in the field of the Earth
by means of artificial satellites is a very demanding task because of the
various other perturbing forces of gravitational and non-gravitational origin
acting upon them. Among the gravitational perturbations a relevant role is
played by the Earth solid and ocean tides. In this communication I outline
their effects on the detection of the Lense-Thirring drag of the orbits of
LAGEOS and LAGEOS II, currently analyzed, and the proposed GP-C experiment
devoted to the measurement of the clock effect.
