Risk classification refers to the use of observable characteristics by insurers to group individuals with similar expected claims, compute the corresponding premiums, and thereby reduce asymmetric information. An efficient risk classification system generates premiums that fully reflect the expected cost associated with each class of risk characteristics. This is known as financial equity. In the health sector, risk classification is also subject to concerns about social equity and potential discrimination. We present different theoretical frameworks that illustrate the potential trade-off between efficient insurance provision and social equity. We also review empirical studies on risk classification and residual asymmetric information.