[en] The kinetics of electron capture by CH₃Br was investigated using the electron swarm method. Carbon dioxide and ethylene were used as carrier gases. The rate constant obtained for thermal electron attachment is equal (in both carrier gases) to (5.3±0.1) x 10^-12cm³ molecule^-1 s^-1. The electron attachment mechanism and kinetics in the mixture containing CH₃Br and H₂S with CO₂ as a carrier gas were also investigated. The rate of this process was found to be formally of the fourth order. The mechanism involving van der Waals complexes (CH₃Br·H₂S) is proposed. The rate constants for the process as well as the lifetime of the complex negative ion were calculated. (author)