Lean principles have attracted the attention of software development companies due to their potential to improve competitiveness. However, the application of such principles in the software domain is still in its infancy. This paper presents a proposal for adapting the Lean Enterprise Self-Assessment Tool (LESAT) to guide the transformation of software development companies toward Lean. LESAT, developed by the Lean Advancement Initiative (LAI) at the Massachusetts Institute of Technology (MIT), has been widely used in other domains. In this study, concepts and expressions of LESAT were analyzed and mapped to software development following the ISO/IEC 12207 standard. Seven assessment items concerning life-cycle processes were modified from the original LESAT. The modified LESAT for software was compared with a lean assessment approach called "Lean amplifier, " which has been developed and successfully used in practice by Ericsson RaD in Finland. The results indicated that LESAT may complement lean assessment in the software domain at enterprise level, involving the entire value stream. Moreover, they clearly emphasized the role of leadership in the transformation.