Direct l-type doubling transitions in the v 6 = 1 state of CF 3 7 9 Br, CF 3 8 1 Br and CF 3 I have been observed using the technique of Fourier transform microwave spectroscopy in the range 4.5-8 GHz. The transitions covered a range of J values from 38-47 for both isotopomers of CF 3 Br and from 40-51 for CF 3 I. The transition frequencies including hyperfine structures could solely be explained by the Δk = ±2, Δl = ±2) l-type resonance interaction including rotation-vibration, quadrupole and spin-rotation terms.