The synthesis of the seven isomeric methyl chlorooctanoates is reported, in most cases for the first time, and their spectral characteristics are described and studied. Hypotheses are advanced to explain the abnormal spectral behaviour of some of them. The mass spectra show scrambling of hydrogen/chlorine and/or the chain carbons, as well as low ability to undergo the McLafferty rearrangement, in some cases. A complete set of 13C NMR parameters is presented, including substituent effects for all positions, which are found to be exceptionally coherent within the series, except for three values. © 1978.