A SIGNIFICANT parties of prebiotic organic matter on the early Earth may have been introduced by carbonaceous asteroids and comets.1The distribution and stable‐isotope composition of individual organic compounds in carbonaceous meteorites, which are thought to be derived from asteroidal parent bodies, may therefore provide important information concerning mechanistic pathways for prebiotic synthesis2and the composition of organic matter on Earth before living systems developed.3Previous studies11,12have shown that meteorite amino acids are enriched in13C relatives to their terrestrial counterparts, but individual species were not distinguished. Here we report the13C contents of individual amino acids in the Murchison meteorite. The amino acids are enriched in13C, indicating an extraterrestrial origin. Alanine is not racemic, and the13C enrichment of its D‐ and L‐enantiomers implies that the excess of the L‐enantiomer is indigenous rather than terrestrial contamination, suggesting that optically active materials were present in the early Solar System before life began. ©1996 American Institute of Physics.