We present an approach to decomposing legacy systems written in procedural languages into objects. The identification of the objects is centred around persistent data scores, such as files or tables in the database, while programs and subroutines are candidate to implement object methods. The approach proposed for assigning programs and subroutines as object methods exploits object oriented design metrics. The rationale behind this choice is that any object oriented decomposition of a legacy system should not lead to a poor design, as this would make the reengineered system more difficult to maintain.