Preliminary results of the optical observations of three microquasars

About 15 microquasars have been discovered up to now. Since 1992, we have established a long-term program to monitor in optical and near-infrared bands the variability of 20 X-ray binaries, including several microquasars. The main goal of this program is to search for clues of the interaction between compact stars and their mass-donor stars, and to learn more about the multiwavelenth properties of X-ray binaries. We present the preliminary results of the observations of three microquasars in the optical band during our long-term program.