Comments are given on a number of papers dealing with principles and procedure in stratigraphic classification which have appeared in British journals during 1963-65. It is emphasized that a clear distinction should be made between biostratigraphic units--bodies of rock strata characterized by certain paleontological features and bounded by the limits of known occurrence of such features--and chronostratigraphic units--bodies of rock strata characterized by representing the rocks formed during certain time-spans of earth history and bounded above and below by isochronous surfaces. Biostratigraphic zones and the chronostratigraphic terms chronozone and stage are discussed.

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