Reference values (norms) of many somatic variables are indispensable in diverse areas, e.g. medicine, sports, armed forces, etc. Such norms are usually presented as means and standard deviations or as lower/upper limits for various age categories of given sex and mostly represent population values instead of being related to body size.

The aim of this paper is to present the most common errors in the process of establishing norms, not only those related to somatic measurements. A set of rules is proposed that may greatly facilitate that process and make the resulting norms rational and reliable.