A method to authorize or authenticate a user of a wireless telecommunication system (32), and includes steps of (a) selecting a word at random from a set of reference words, or synthesizing a reference word; (b) prompting the user to speak the reference word; and (c) authenticating the user to operate in, or through, or with a resource reachable through the wireless telecommunication system, only if the user's speech characteristics match pre-stored characteristics associated with the reference word. In one embodiment the steps of selecting or synthesizing, prompting, and authenticating are performed in a mobile station (10) having a speech transducer (19) for inputting the user's speech, while in another embodiment at least one of the steps of selecting or synthesizing, prompting, and authenticating are performed in a wireless telecommunications network (32) that is coupled between the mobile station and a telephone network (35). In yet another embodiment at least one of these steps are performed in a data communications network resource (38) that is coupled through a data communications network (37), such as the Internet, and the wireless telecommunications network to the mobile station. The step of prompting may include a step of displaying alphanumeric text and/or a graphical image to the user using a display (20) of the mobile station.