Visual observation of high-pressure, high-temperature steam/water two-phase flow is of interest for many engineering applications. It is particularly so when complicated phase-change and phase separation/mixing processes are involved. This paper is concerned with development of cooling-free small-sized video probes which withstands high-pressure steam/water two-phase flow. The probe uses optical glass fiber for both lighting and observation. To obtain a clear image, several technical problems were resolved, including light intensity, window material corrosion and thermal expansion. These are discussed in relation to practical experiences with experimental facilities which simulate thermal-hydraulics condition during a loss-of-coolant accident (LOCA) of a pressurized water reactor (PWR) at pressures ranging up to 18MPa and temperatures up to 630K.