This thesis reports the preparation of a range of guandine and guanidinium species used as catalysts for asymmetric Michael additions. The most successful of these were based on the generalized structure I (R = Me, iPr, Bn, Cy; R1, R2 = H, Me, Ph, 1,2-phenyl, R3 = Me, Bz, Cbz, Ph) and were effective catalysts of the reaction between of 2-nitrostyrene 52 and 93 leading to yields 35-99 % and up to 44 % enantiomeric excess for the product 94. Similar reactions using diethyl malonate or 2,4-pentanedione were also catalysed however these were less successful and generally led to low enantiomeric excesses and the formation of unidentifiable polymeric byproducts. X-ray crystallographic structures were determined for several of these compounds and the hydrogen bonding patterns observed were used to speculate on the mechanism of the reaction and the magnitude of the asymmetric induction.