[en] A formal calculated estimate of total mutagenic effectivity of ¹⁴C evenly distributed in the carbon of organism is presented as a statement of the problem. The value obtained is at least 4000 which is 2 to 3 orders of magnitude greater than the experimental values for ¹⁴C found by other authors. Possible reasons for such discrepance are presented. It is suggested that natural radiocarbon may be one of the basic natural mutagens and sources of gene pool replenishment. The use of ¹⁴C as an effective mutagen in radiation selection is proposed