Introduction 2 Fermentation and Isolation 3 Structure Determination 4 Biosynthesis 5 Metabolism 6 Chemistry 6.1 Total Synthesis 6.2 Partial Synthesis 6.3 The Interconversion of the Avermectins and Mil bemycins 6.4 Protection and Acylation 6.5 Oxidations 6.6 Alkylation 6.7 Reduction 6.8 Avermectin Aglycons and their Monosaccharide Analogues 7 Structure-Activity Relationships 8 Conclusion 9 References* Wherever avermectins are described in this Report by using only the first two identifying characters, as in A2, this refers to mixtures of the a and b analogues. In these cases, only the structure of the major component is indicated in the diagram. Where fully identified, as in B2b, this implies the use of pure compound.