The paper provides a brief overview of the present state-of-the-art in the field of the critical heat flux (CHF) in subcooled flow conditions, with particular regard to high liquid velocity and highly subcooled conditions. These thermofluid-dynamic conditions to reach very high values of the CHF (up to 80 MW/m2) as requested by fusion technology requirements. After reporting the general features of the problems, some details are given about the main parameters affecting CHF in subcooled flow boiling (subcooling, pressure, duct diameter and length, fluid velocity, duct orientation and flow direction, heat flux distribution), and the respective knowledge and possible enhancement techniques for CHF (extended surfaces, hypervapotron, surface roughness, swirl flow, helically coiled wires) are reviewed. As fundamental aspects of highly subcooled flow boiling are not known and, on the other hand, such knowledge is necessary for any possible enhancement technique evaluation and for a theoretical modelling of the phenomenon, recent experiments carried out over the last five years on CHF in subcooled flow boiling are reviewed together with the main correlations and models currently used for data prediction, and suggestions for particular and general research guidelines are given.