Social rating agencies (SRAs) use corporate social performance (CSP) metrics to evaluate the way business organizations deal with social and environmental issues. In producing their social ratings, SRAs can operate as ‘economic actors’ or ‘social actors’. As very little is known on how they construct their metrics, this chapter lifts the veil on the rating practices of a well-established social rating agency (SRA), oekom research AG. Key aspects of this SRA’s relationships and interactions with internal and external actors show how the construction process of social ratings becomes standardized, and how the communicative practices around the making of these ratings offer new insights into CSP scholarship, and into management and organization studies. The chapter comprises four sections: 1) an overview of the literature addressing SRAs, 2) the sociogenesis of oekom research AG (oekom), 3) an overview of oekom’s rating practices, and 4) a discussion and conclusion.