Flares in RS CVn stars

The observational aspects of the flare events in RS CVn binaries are reviewed. The main results from observations in the optical continuum, optical and UV lines, X-ray and radio wavelengths suggest that outbursts are time linked at all spectral bands. Physical parameters of flares and VLBI measurements indicate that flares take place in regions of the stellar size with typical conditions: 1) electron energy E 1-10 MeV; 2) magnetic field B 30-50 Gauss; 3) ambient thermal gas densities n approx. = 10 cm-3. Occurrence of flares in Algol and UMa systems are discussed in the context of the RS CVn phenomena they present. (author)