Abstract Equality of opportunity is a widely accepted principle of distributive justice and it is the leading idea of most political platforms in several countries. According to this principle, a society might institute policies that secure an equal distribution of the means to reach a valuable outcome among its members. Once the set of opportunities have been equalized, which particular opportunity, the individual chooses from those open to her, is outside the scope of justice. Ex ante inequalities, and only those inequalities, should be eliminated or compensated for by public intervention. The recent literature on the opportunity egalitarianism often merges these questions introducing two different economic issues. On one side the design of a public policy intended to implement the equality of opportunity view and on the other side the problem of measuring the degree of opportunity inequality in a society. We describe the basic setting and assumptions of some different approaches derived by Roemer’s algorithm for public policy and then we discuss some theoretical and empirical studies to separate and test alternative paradigms on the measurement of inequality of opportunity. Accordingly, an extended critique on the causality issue on policies and measurements is taken into account.