<p>Economic inequality is substantial and is rising in many countries. The existence of inequality has been a cause for concern throughout history, but only more recently has the availability of empirical data afforded academics the ability for more rigorous investigation. The impact of economic inequality on health has been one key area of this inquiry, developing and testing the income inequality hypothesis (IIH) – that income inequality is a wide-ranging and detrimental determinant of health outcomes. The literature on this topic is reviewed and implications for social work research are discussed. This article presents an overview and critical review of theoretic and empirical literature on economic inequality and the income inequality hypothesis, examining prior systematic reviews of the literature and assessing new empirical evidence in the field. It finally reviews the social work research contributions to the field. Literature appearing recently is largely consistent with prior systematic reviews in support of the IIH. Social work research has made comparatively little contribution to the study of the health impacts of economic inequality. The article invites social work researchers to the economic inequality research domain, calling on them to bring their efforts to bear on this important area of inquiry, which is central to the social work grand challenges and the mission of social work at large.</p>