GRAVITATIONAL MICROLENSING IN THE LOCAL GROUP

The status of searches for gravitational microlensing events of the st ars in our galaxy and in other galaxies of the Local Group, the interp retation of the results, some theory, and prospects for the future are reviewed. The searches have already unveiled similar to 100 events, a t least two of them caused by binaries, and have already proven to be useful for studies of the Galactic structure. The events detected so f ar are probably attributable to the effects of ordinary stars, and pos sibly to substellar brown dwarfs; however, a firm conclusion cannot be reached yet because the analysis published to date is based on a tota l of only 16 events. The current searches, soon to be upgraded, will p robably allow determination of the mass function of stars and brown dw arfs in the next few years; these efforts will also provide good stati stical information about binary systems, in particular their mass rati os. They may also reveal the nature of dark matter and allow us to det ect planets and planetary mass objects.