The invention concerns a method for the administration of a subscriber SIM card 3 inserted in the main smartcard reader of a mobile telephone of the type including a second smartcard reader, using an additional administrator smartcard temporarily inserted in this second reader. The administrator smartcard includes at least one specific loader (Ch) applet and one or more files (f.sub.1-f.sub.n) corresponding to the applets (A.sub.1-A.sub.n) which can be loaded in the SIM card under the control of the loader (Ch). The administrator card complies with the Sim Toolkit standard. The method can also be used to carry out the deletion, modification and various operations on data or applets (A.sub.1-A.sub.n) present in the SIM card: display, determination of the memory space, etc.The invention also concerns an embedded system, more particularly a smartcard, for the implementation of the method.