A method for a mobile station (MS) to acquire system information of other communication systems via an initial entry communication system in which the mobile station (MS) initially enters via a base station (BS) is disclosed. The BS can deliver system information using a message transmitted to the MS at each frame or at intervals of a periodic time. In other words, the BS delivers specific information indicating whether the system is supported or not in a message. If the system is supported, the BS transmits a message including the system information to the MS. During or after the initial entry, the BS may deliver the system information using messages communicated with the MS. Namely, the BS can voluntarily or on the MS′ demand transmit a message including the system information to the MS indicating whether the system is supported.