Diffusion coefficients of potassium chloride in potassium chloride solutions of molality (0, 1, 2.5, and 4.5) mol.kg(-1) were measured at temperatures of (298.15, 323.15, 348.15, 373.15, and 423.15) K and at pressures from (0.1 to 69) MPa using the Taylor dispersion technique. The results have an overall estimated expanded relative uncertainty of 1.6 % with a coverage factor k = 2. When compared with standard reference data for the diffusion coefficient of KCl in KCl solutions at T = 298.15 K and p = 0.1 MPa, a relative deviation of 0.5 % is observed. The effect of pressure was found to be very small. A satisfactory multiparameter correlation of all of the data in terms of pressure, temperature, and molality was obtained; this exhibits an absolute average relative deviation of 1.2 % in comparison with our data. The model also provides a good account of the majority of the data available in the literature.