  Microlensing events are usually selected among single-peaked non-repeating
light curves in order to avoid confusion with variable stars. However, a
microlensing event may exhibit a second microlensing brightening episode when
the source or/and the lens is a binary system. A careful analysis of these
repeating events provides an independent way to study the statistics of wide
binary stars and to detect extrasolar planets. Previous theoretical studies
predicted that 0.5 - 2 % of events should repeat due to wide binary lenses. We
present a systematic search for such events in about 4000 light curves of
microlensing candidates detected by the Optical Gravitational Lensing
Experiment (OGLE) towards the Galactic Bulge from 1992 to 2007. The search
reveals a total of 19 repeating candidates, with 6 clearly due to a wide binary
lens. As a by-product we find that 64 events (~2% of the total OGLE-III sample)
have been miss-classified as microlensing; these miss-classified events are
mostly nova or other types of eruptive stars. The number and importance of
repeating events will increase considerably when the next-generation wide-field
microlensing experiments become fully operational in the future.
