  We review the results of the 1988 multi-wavelength campaign on the late-type
eclipsing binary YY Geminorum. Observations include: broad-band optical and
near infra-red photometry, simultaneous optical and ultraviolet (IUE)
spectroscopy, X-ray (Ginga) and radio (VLA) data. From models fitted to the
optical light curves, fundamental physical parameters have been determined
together with evidence for transient maculations (spots) located near
quadrature longitudes and intermediate latitudes.
  Eclipses were observed at optical, ultraviolet and radio wavelengths.
Significant drops in 6cm radio emission near the phases of both primary and
secondary eclipse indicate relatively compact radio emitting volumes that may
lie between the binary components. IUE observations during secondary eclipse
are indicative of a uniform chromosphere saturated with MgII plage-type
emission and an extended volume of Ly$\alpha$ emission.
  Profile fitting of high-dispersion H alpha spectra confirms the chromospheric
saturation and indicates significant H$\alpha$ opacity to heights of a few
percent of the photospheric radius. There is evidence for an enhanced H alpha
emission region visible near phase 0.25-0.35 which may be associated with a
large spot on the primary and with two small optical flares which were also
observed at other wavelengths: one in microwave radiation and the other in
X-rays. For both flares, L_X/L_opt is consistent with energy release in closed
magnetic structures.
