In recent years a great deal of attention has been paid to the determination of chemical bond energies. This has been due to a variety of factors, one important reason has been the development during the last twenty years of ideas about the detailed molecular interactions which take place during the process of chemical change. Since chemical change involves the making and breaking of bonds, either as separate or simultaneous processes, it is clear that progress from qualitative to quantitative explanations of chemical interactions will be greatly assisted by more precise knowledge of the strength of the links in the individual molecules. The early tables of bond energies (of Pauling) laid more emphasis on the approximate constancy of the values for any bond in various molecules than on variation from the mean. Chemical intuition on the other hand, would suggest that the difference in the reactivity of say CH₃.CH₂.C1 and CH₃.C00C1 might be due chiefly to some difference in the strength of the C-C1 links. More recent work substantiates this and has provided evidence from various sources to show how bond energies for certain links depend on their molecular environment. In the following pages a survey is given of the methods which have been employed for this purpose and some of the results achieved.