Résumé : Oscillations of B0s mesons were studied in events with a large transverse momentum lepton selected from 3.2 million hadronic Z0 decays registered by DELPHI between 1991 and 1994. A limit on the mass difference between the physical B0s states Δms > 6.5ps-1 at 95% C.L. was obtained by combining the results obtained in three channels. © 1997 Published by Elsevier Science B.V.