The population approach is well recognized as an effective strategy to improve population health, as well as the population-at-risk approach. It aims to decrease risk exposure of the total population through a change of contextual conditions. However, the population approach has the possibility of increasing health inequality because of variation in the effectiveness of the strategy in accordance with the risk exposure. This paper proposes the “vulnerable population approach” as an alternative and supplemental strategy. It aims to decrease health inequalities between socially defined groups, by shifting the distribution of a lower level of risk exposure of the groups through changes in social and environmental conditions that make groups at higher risk. No interventional approach can be singly applied to all health problems. To improve population health, it is important to select the most effective strategy among the three approaches, considering their advantages and limitations, and to adopt a suitable combination of different approaches.