The term "low-grade glioma" historically refers to adult diffuse gliomas that exhibit a less aggressive course than the more common high-grade gliomas. In the current molecular era, "low-grade" refers to World Health Organization central nervous system grade 2 gliomas almost always with an isocitrate dehydrogenase (IDH) mutation (astrocytomas and oligodendrogliomas). The term "lower-grade gliomas" has emerged encompassing grades 2 and 3 IDH-mutant astrocytomas and oligodendrogliomas, to acknowledge that histological grade is not as important a prognostic factor as molecular features, and distinguishing them from grade 4 glioblastomas, which lack an IDH mutation. These grades 2 and 3 IDH-mutant tumors are characterized by indolent growth but are ultimately incurable in most cases, presenting significant management challenges. Physicians must carefully weigh all available evidence to balance improvements in survival from new treatments against treatment toxicities. This review summarizes the evidence guiding the treatment of these patients.