Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), corresponds with a heterogeneous group of mature T-cell lymphomas. Recent gene expression profiling studies have identified at least two molecular subgroups (GATA3 and TBX2). Standard treatment and outcomes remain poor. High-dose chemotherapy with autologous stem cell transplantation is incorporated into primary therapy for young fit patients but remains ineffective for most and has not been tested in a randomized study. Several novel agents have been approved for use in relapsed/refractory PTCLs, and although response rates are modest for most, durable remissions have been reported. Selecting rationale combinations and incorporating predictive biomarkers will be important moving forward to improve outcomes in patients with PTCL.