Using well defined input pulses the amplification by stimulated thermal Rayleigh scattering was investigated experimentally as a function of time (within the pulse), of absorption coefficient, and of interaction length. The frequency difference between the two interacting light pulses was varied with an accuracy better than Δν/ν = 10-8. Amplification was measured in the backward direction and at several degrees from the forward direction. The various experimental observations are in good agreement with theory. The possibility of determining material parameters in this amplifier system is discussed