Abstract: A method and arrangement for limiting the use of a mobile telephone is characterized in that it involves setting a time limit (TIMER.sub.-- VALUE) in said mobile telephone (20). The time limit can be set for accumulated operating time or elapsed time in general. Setting of the limit is advantageously made possible by means of a secret code (SECRET.sub.-- KEY). Thereafter, the mobile telephone begins measuring time, and when the elapsed or accumulated time reaches the set limit, operation of the mobile telephone (20) is blocked. Then, only operation by which a new time limit can be set or the block can be removed is allowed. A mobile telephone manufacturer can easily realize an arrangement according to the present invention in a mobile telephone, and said arrangement can just as easily be implemented by, for example, a mobile telephone renter. The temptation to misuse and steal mobile telephones decreases when it is known that said telephones have a limited operating time, after which they will not function.