The aziridination of olefins with {(4-nitrophenylsulfonyl)imino}phenyl-l3-iodane, NsNTIPh (1c), in the presence of [Rh2(OAc)4] proceeds in yields of up to 85% when the olefin is used in large excess. Under optimized conditions, styrene (4a) is aziridinated with 1 equiv. of NsNTIPh (1c) in 64% yield with 2 mol% of catalyst. The aziridines derived from electron-rich olefins undergo ring-opening under the conditions of the aziridination and afford rearrangement products or pyrrolidines. The aziridination is sterospecific with 1,2-dialkyl- and 1,2-arylalkyl-disubstituted olefins, but nonstereospecific with stilbene.The r-value for aziridination of substituted styrenes is –0.61. No ring-opened products are observed upon aziridination of vinylcyclopropanes. In the presence of chiral RhII catalysts, the aziridination is enantioselective, affording an ee of 73% with cis-b-methylstyrene (4k) and Pirrungs [Rh2{(R)-(–)-bnp}4] catalyst. The experimental results are consistent with a one-step mechanism for transfer of the nitrenoid moiety from the catalyst to the olefin.