The lowest frequency fundamental band ν3 of CD3Br has been studied at a resolution limit of 0.03 cm-1. About 250 J lines belonging to both isotopic species CD379Br and CD381Br have been measured in the P and R branches of this parallel band. In the analyses, leastsquares fits and simulations have been applied. The band centers, 577.286(2) and 575.975(2) cm-1, respectively, have been obtained together with B, DJ, and α3A values. In addition to the main bands, the hot bands 2ν3 - ν3 and ν3 + ν6 - ν6 have been investigated. © 1979.