AbstractIn this paper primariLy the pecuLiarities of physicaL systems that affect the whoLe process of modeL formation are presented.Approaches to the choice of regression criterion based on numericaL mathematics–theory of approximation–, mathematicaL statistics–theory of point estimates–as weLL as heuristic search are discussed. Attention is paid to the fact how the particuLar approaches affect interpretation of modeL parameters. In simpLe practicaL exampLes it is demonstrated that in some cases the optimaL criterion cannot be chosen beforehand.FinaLLy, a simpLe program for HP 9825 A desk top computer enabLing to soLve generaL regression probLems by using an arbitrary regression criterion is described.