The ages of recent effusive eruptions on Erebus volcano, Antarctica are poorly known. Published Ar-40/Ar-39 ages of the 10 youngest "post-caldera" lava flows are unreliable because of the young ages of the flows (<10 ka) and the presence of excess Ar-40. Here we use cosmogenic He-3 and Cl-36 to provide new ages for the 10 youngest flows and 3 older summit flows, including a newly recognized flow distinguished by its exposure age. Estimated eruption ages of the post-caldera flows, assuming no erosion or prior snow cover, range from 4.52 +/- 0.08 ka to 8.50 +/- 0.19 ka, using Lifton et al. (2014) to scale cosmogenic production rates. If the older Lal (1991)/Stone (2000) model is used to scale production rates, calculated ages are older by 16-25%. Helium-3 and chlorine-36 exposure ages measured on the same samples show excellent agreement. Helium-3 ages measured on clinopyroxene and olivine from the same samples are discordant, probably due in part to lower-than-expected He-3 production rates in the Fe-rich olivine. Close agreement of multiple clinopyroxene He-3 ages from each flow indicates that the effects of past snow coverage on the exposure ages have been minimal. The new cosmogenic ages differ considerably from published Ar-40/Ar-39 and Cl-36 ages and reveal that the post-caldera flows were erupted during relatively brief periods of effusive activity spread over an interval of similar to 4 ka. The average eruption rate over this interval is estimated to be 0.01 km(3)/ka. Because the last eruption was at least 4 ka ago, and the longest repose interval between the 10 youngest eruptions is ka, we consider the most recent period of effusive activity to have ended.