The reaction Cl + HI --> HCl + I was investigated using the laser-photolysis/resonance fluorescence method to monitor (i) the disappearance of atomic Cl and (ii) the growth of atomic I. The results were similar, and together yield the rate constant k = (3.4 +/- 1.4) x 10(-11) exp (+2.8 +/- 1.1 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) (1sigma errors) over 297-390 K. The 95% confidence limits for k are +/-19%. Another approach, discharge/fast-flow (iii), with monitoring of the consumption of Cl in the presence of excess HI, yields k = 1.2 x 10(-10) cm(3) molecule(-1) s(-1) at 298 K, with 95% confidence limits of +/-17%. The results are in accord with each other and with most literature data. This indicates that monitoring of the formation of the atomic halogen product in this example of a radical abstraction of H from a hydrogen halide is reliable.