The errors in primary production estimation by the radiocarbon method may differ from one trophic region to another. Such supposition is based on unequal phytoplanktonic structural characteristics of these regions. These errors are likely to appear rather significant in oligotrophic waters predominated by nano- and ultranano-plankton (the so-called picoplankton). The organic substance of oligotrophic waters is obviously produced by picoplankton for the most part, the need for clarifying possible errors when estimating primary production by the radiocarbon method, which is the purpose of the present work is urgent. For these topics in oligotrophic waters, measurements were carried out in two ways: (1) according to the generally accepted pattern (Sorokin, 1956, 1958) and (2) with the use of methodical experiments aimed at modifying that pattern.