Distributed temperature sensing based on time-correlated two-photon excited fluorescence (TPF) in doped fibre is described. Counter-propagating laser pulses generate a TPF flash at the position of overlap which is scanned along the fibre by a variable relative time delay. The flash is detected and analysed at one end. With the fluorescence power being completely independent of excitation pulse duration and temporal profile, the sensor does not require ultrashort excitation pulses for operation. There is potential for high spatial resolution as the length of the sensed region depends only on pulse duration. TPF is reported in bulk glass doped with rare earths and in doped single-mode fibre. The suitability of fluorescence transitions for sensing is discussed taking into account the temperature dependence of the decay times, the location of the terminating energy level relative to the ground state, and the option of non-degenerate TPF.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.