Commentary and analysis of the problem whether courts should consider the “maturity” of claims or the litigation history of claims in the process of evaluating whether to certify a proposed class action. The “maturity” factor refers to a consideration of whether the particular claims asserted in a class action have been previously litigated in individual litigation, to reveal a pattern of plaintiff or defendant wins or losses in such cases. The “maturity” factor has had particular salience in mass tort litigation. The theory is that if defendants have consistently won in individual suits, this suggests that the claims are weak or meritless, and therefore courts should be reluctant to certify a class action and provide settlement leverage to plaintiffs (in light of otherwise weak claims). On the contrary, if the trial of individual lawsuits reveals a pattern of plaintiff victories, this suggests that the litigation is “mature,” thereby supporting a motion for class certification. The requirements for establishing a class action under Rule 23 do not contain any explicit provision that mandates a court to consider the maturity of the claims or the litigation. The is article surveys views with regard to imposition of a maturity factor in the class certification calculus, including existing authoritative treatises such as the Manual for Complex Litigation, federal court decisions endorsing and rejecting the maturity factor, and legislative proposals to codify a maturity factor into Rule 23.