The economic implication of the maintenance phase of software development process can be managed by using software metrics to build maintainability quality into software products. Several software quality models and maintainability measurement models/methods have been proposed in the literatures, still the evaluation of Object-Oriented Software (OOS) maintainability has not attained uniformity and consistency in measurement results. This paper reviews existing studies in OOS maintainability measurement within the past decade. Results show that elements of subjectivity in the measurement methods threaten the attainment of uniformity, consistency and potential wide acceptability of the identified models in this review. © 2012 IEEE.