Unified Process - UP, is a prescriptive framework widely used by the software industry. Since the UP was developed under the assumption of a universal applicability, its definition is not match to every organization or project. Several proposals have been outlined to adapt this framework to the specific needs of organizations and projects. Although these adaptations have been applied in contexts, industry and research, they do not include systematic mechanisms and so, they are difficult to replicate. This paper applies a general strategy, but concrete to facilitate systematic adaptation of the Unified Process using a software process line approach. In order to evaluate this proposal, the UP implementation discipline has been modeled as a software process line using CASPER meta-process providing evidences about the advantages and disadvantages of approach.