Diazo decomposition of allylic and homoallylic diazoacetates 10a-p and 22a-j catalyzed by chiral dirhodium(II) tetrakis[methyl 2-pyrrolidone-5(S)-carboxylate], Rh-2(5S-MEPY)(4) (7), and its enantiomer, Rh-2(5R-MEPY)(4) (8), produces the corresponding intramolecular cyclopropanation products 11a-p and 23a-j in good to excellent yields and with exceptional enantioselectivity. Higher enantiocontrol is observed with allylic diazoacetates than with their homoallylic counterparts, but allylic diazoacetates are subject to greater variations in enantioselectivities with changes in substitution patterns on the carbon-carbon double bond. For example, the enantioselectivities in the intramolecular cyclopropanations of 3-alkyl/aryl-2(Z)-alken-1-yl diazoacetates are generally greater than or equal to 94%, whereas the cyclizations of the homologous 4-alkyl/aryl-3(Z)-alken-1-yl diazoacetates are typically in the range of 70-90% ee. The corresponding 3-alkyl/aryl-2(E)-alken-1-yl and 4-alkyl/aryl-3(E)-alken-1-yl diazoacetates undergo cyclization with slightly lower ee’s (54-85%). Although the Rh-2(5S-MEPY)(4)-catalyzed cyclization of the 2-methallyl diazoacetate 10c proceeds with only 7% ee, alternative chiral dirhodium(II) catalysts, including those with methyl N-acylimidazolidin-2-one-4(S)-carboxylate ligands such as Rh-2(4S-MACIM)(4) (14) and Rh-2(4S-MPAIM)(4) (15), may be employed to increase the level of enantiocontrol to 78 and 65%, respectively.