Search for lepton flavour number violating Z(0)-decays

A search for lepton flavour number violating Z(0) decays in the channels Z(0) --> mu tau, Z(0) --> e tau, Z(0) --> e mu, using the DELPHI detector with data collected during the 1991-94 LEP runs, is described, No signal was found. Upper limits at 95% confidence level for the respective branching fractions of 1.2 x 10(-5), 2.2 x 10(-5), and 0.25 x 10(-5), were obtained.