Ethane oxidation at intermediate temperatures and high pressures has been investigated in both a laminar flow reactor and a rapid compression machine (RCM). The flow-reactor measurements at 600-900 K and 20-100 bar showed an onset temperature for oxidation of ethane between 700 K and 825 K, depending on pressure, stoichiometry, and residence time. Measured ignition delay times in the RCM at pressures of 10-80 bar and temperatures of 900-1025 K decreased with increasing pressure and/or temperature. A detailed chemical kinetic model was developed with particular attention to the peroxide chemistry. Rate constants for reactions on the C 2 H 5 O 2 potential energy surface were adopted from the recent theoretical work of Klippenstein. In the present work, the internal H-abstraction in CH 3 CH 2 OO to form CH 2 CH 2 OOH was treated in detail. Modeling predictions were in good agreement with data from the present work as well as results at elevated pressure from literature. The experimental results and the modeling predictions do not support occurrence of NTC behavior in ethane oxidation. Even at the high-pressure conditions of the present work where the C 2 H 5 + O 2 reaction yields ethylperoxyl rather than C 2 H 4 + HO 2 , the chain branching sequence CH 3 CH 2 OO −→ CH 2 CH 2 OOH +O 2 −→ OOCH 2 CH 2 OOH → branching is not competitive, because the internal H-atom transfer in CH 3 CH 2 OO to CH 2 CH 2 OOH is too slow compared to thermal dissociation to C 2 H 4 and HO 2 .