  The CDF and D0 experiments have measured single and double top quark
production in ppbar collisions at the Tevatron at a centre-of-mass energy of
1.96TeV. The applied methods are used to constrain properties of the top quark
and to search for new physics. Several methods of signal to background
separation and of the estimation of the background contributions are discussed.
Experimental results using an integraged luminosity up to 5.3fb^-1 are
presented.
