The paper shows how high-precision temperature (HPT) logging and numerical temperature modelling for radial flow injection (TERMOSIM) assess the performance of water injection wells, and outlines specific features of modern temperature logging tools and logging procedures. The basic principles and critical elements of temperature modelling for injection wells are discussed. The paper presents five cases illustrating how the fitting of a numerical model to actual temperature logs can be used to describe the injection pattern including complicacies caused by behind-casing channelling. Particular attention is given to how temperature logging and modelling complement information obtained by the conventional PLT technique based on the mechanical spinner. The concept and basic features of the TERMOSIM temperature modelling software are given in the Appendix.