[en] This paper provides a review of the evaluation of natural circulation in the Fast Flux Test Facility (FFTF), a loop type reactor plant. The emphasis is on the role of natural circulation in decay heat removal; however, free convection during either operation at power or normal shutdown does influence some aspects of the design and these are mentioned. In treating decay heat removal the topics discussed include steady state loop performance and transient dynamics for conditions immediately after scram and for the longer term which involves different considerations. The review summarizes complex dynamics, specific to the FFTF design evaluation, which particularly illustrate large available margins for decay heat removal (possibly involving coolant boiling). Also addressed are modelling considerations and the status of experimental programs. To date, design adequacy has been assessed largely by a combination of component tests and system analyses, with design margins increased to accommodate uncertainties. Presently planned tests, when completed, will provide an empirical base for characterizing system dynamic behavior in the range most relevant to current LMFBR designs and will demonstrate FFTF decay heat removal capability directly