After short discussion of the definition of the «ageing» term the one for the «cellular ageing» with special emphasis on the models for studying the process in Metazoa is proposed. The in vitro models currently used in cellular ageing researches are briefly reviewed and the advantages of using prokaryotic, organisms and in particular, cyanobacteria (the blue-green algae) in the kind of research are critically analysed. Besides of general advantages of unicellular and prokaryotic organism models (absence of specialized, «metazoan», cellular functions, lack of problems with the extrapolation of in vitro results on in vivo situations, the possibility to use simple synthetic growth media with completely controlled composition, great phylogenetic distances from macroorganism cells commonly used in cellular ageing research (what is valuable in terms of comparative gerontology) and simplicity of organization) these are the following ones: the greatest primitivity, the probability to induce «pure» autotrophy or heterotrophy in the same organism, relative independence of growth characteristics on culture conditions, presence of close taxonomically related unicellular and pseudo-multicelluar forms and the «unusual» spectrum of sensitivity to various external factors. The close relationship between cellular ageing and proliferation activity with the special reference to the «stationary phase ageing» model is emphasized.