  We briefly summarize the observational properties of ultra-compact binaries
called AM CVn stars. We analize their outbursts originating from the
thermal-viscous instability in helium accretion disc. We present our
preliminary results in applying the model of Dwarf Novae outbursts to helium
discs. We can calculate models of outbursts of reasonable amplitude of 2 mag
with a constant alfa parameter throughout the calculation. Setting the mass
transfer rate close to its upper critical value produces model lightcurves that
resemble short superoutbursts.
