A comprehensive study of the sources of systematic errors in the measurements of retention times has been made. These sources include measurement errors, which are related to the problems of time measurements and are usually small and easy to correct and instrumental errors which are more difficult to correct and eventually limit the accuracy of the measurements. The main sources of systematic, instrumental errors are the retention of the inert peak (compounds which are easy to detect are not completely inert) and the effect of carrier gas volumes outside the column. These two factors are easy to correct in principle, but the random errors made in the determination of the parameters necessary to Calculate these corrections are the main limitations to the present accuracy of retention times measurements