A scarcity of information on the rare‐gas halide trimers makes detailed calculations of their formation rates from the excited rare‐gas halides impossible. However, we have developed an approximate method/model for determining these rate constants. Rate constants for reactions of possible interest for the KrF∗ and XeF∗ laser systems are calculated. These reactions are (1) KrF∗+Rg+Rg′→KrRgF∗+Rg′ and (2) XeF∗+Rg+Rg′→XeRgF∗+Rg′, where Rg, Rg′=Ar, Kr in Eq. (1) and Ne, Ar, Xe in Eq. (2). Results are compared with available experimental data.