Realized almost on a daily basis, psychosocial assessment is a fundamental activity of social work. Rather than examining how we can make better assessment, I'm interested in what assessment is. By doing so, I question its nature, goals and impacts. I hope to give a critical analysis of how assessment manifests itself through the dominant models present in the social workers’ practices. Furthermore I investigate how its epistemological perspective raises ethical issues that must gain our attention so that not only values put forward by this approach are questioned but the organization of Quebec's social services as well.