Understanding of the 1,4-addition of organocuprates, especially LiCuR 2 species, to enone Michael acceptors has blossomed in the light of recent kinetic, NMR, and theoretical investigations. These investigations have been reviewed and are compared to the various reaction coordinates they support. Emphasis is placed on relating the theoretical calculations to physical data extracted from real systems. The mechanism of cuprate conjugate addition is compared to related reactions including: additions to ynones, alkene carbocupration, and S N 2A allylic and propargylic substitution reactions. Scheme 1 Cuprate mediated 1,4-addition of 'MR' to a,b-unsaturated systems (enones). R and Y represent generic groups. The 'E + ' source may be H + , RI, RCHO, etc.