This Bachelor's thesis in Environmental Science studies the quality of an index of performance measurement of Swedish municipalities' sustainability governance offered by the environmental magazine Miljöaktuellt. Executed for six consecutive years, this evaluation is arguably the most comprehensive and widely spread local sustainability assessment in Sweden. Contextualizing this quantitative measurement tool in the paradigm of New Public Management, the research questions posed are: 'to what extent does the index employed by Miljöaktuellt correspond to the requirements of a set of quality criteria for sustainability assessment?' and 'is the index appropriate as a measure of, or a goal for, Swedish municipalities' internal sustainability efforts?' Through the perspective of evaluation theory, Miljöaktuellt's index is seen as a performance evaluation, thus categorizing this study as a meta-evaluation. Through a qualitative thematic approach, the index is analyzed using the 8 BellagioSTAMP-principles that were developed as tools for assessing quality of sustainability assessments as themes for the analysis.