In order to understand the electrostrictive behavior of Pb(Mg1/3Nb2/3)O-3-PbTiO3 (PMN-PT) solid solutions, the dielectric constants, the electric field induced strains, the electric-field induced polarization, and the pyroelectric coefficients of (1-x)PMN-xPT (x = 0.1 similar to 0.4) were investigated in the temperature range -50 degrees C similar to 200 degrees C. For x = 0.1 similar to 0.35, where the phase transition is diffuse, the strain has a maxima at the temperature of maximum pyroelectric coefficient (depolarizing temperature) rather than the temperature of maximum dielectric constant (Curie temperature). For x = 0.4, where the phase transition is relatively sharp, the strain decreases monotonically as the temperature increases. Relationships among the above experimental results are discussed.