This Article proposes a thought-experiment with regard to the administration of class actions. It is almost axiomatic that class actions are determined through a single “certification.” However, class actions can be certified through a tiered certification, e.g., a preliminary certification on a more lenient standard, followed by a full certification. Flattening the certification process allows a richer set of solutions to familiar dilemmas. Currently, a noncertified class does not bar subsequent certification attempts. Focusing on this problem, this Article demonstrates that tiered certification is a superior solution — members of a class that passed the first certification but not the second receive at least minimal procedural protection and thus could be precluded from serial certification attempts. More generally, tiered certification can better handle several species of collective litigation, which can be referred to as semi-class actions. Collective proceedings, whose certification costs are greater than their social benefit, do not justify a comprehensive class treatment. But to the extent that these cases entail some modest social value, they deserve to pass a less onerous, preliminary certification. The Article discusses cases that fit this pattern, for instance prospective, class-wide relief for technical regulatory violations.