Today’s wireless networks are characterized by ?xed spectrum assignment policy. The limited available spectrum and the ine?ciency in the spectrum usage necessitate a new communication paradigm to exploit the existing wireless spectrum opportunistically. This new networking paradigm is referred to as NeXt Generation (xG) Networks as well as Dynamic Spectrum Access (DSA) and cognitive radio networks. Cognitive radio is a paradigm for wireless communication in which either a network or a wireless node changes its transmission or reception parameters to communicate efficiently avoiding interference with licensed or unlicensed users. In practice, the spectrum allocated to licensed primary users is not utilized properly. The secondary unlicensed users can sense and utilize the unutilized spectrum. In this work, a fuzzy logic based system is proposed where the secondary user can opportunistically use the spectrum. The descriptive factors for choosing the proper secondary unlicensed user are distance of secondary user from primary user, velocity of the secondary user and ratio of spectrum to be utilized by secondary user to the total unutilized spectrum. The proposed system is found to give satisfactory results and the user with highest possibility of spectrum access decision is allowed to use the spectrum.