Line intensities as well as self- and nitrogen-broadening coefficients have been determined for 20 transitions in the 2 ν2 and ν4 bands of 14NH 3 using a diode laser spectrometer. Vibrational-inversional transition moments have been determined for transitions from the ground state to the ν2, 2 ν2 and ν4 states by a least-squares fit to the line intensities, taking into account Coriolis and l-type interactions between the nν2 ( n = 1, 2, 3), ν4 and ν2 + ν4 states [Š. Urban, V. Špirko, D. Papoušek, R. S. McDowell, N. G. Nereson, S. P. Belov, L. I. Gershtein, A. V. Maslovskij, A. F. Krupnov, J. Curtis, and K. Narahari Rao, J. Mol. Spectrosc.79, 455-495 (1980)]. The values of these transition moments have been combined with the previously obtained transition moments for NH 3 and its isotopomers to obtain an improved fit to the μz component of the electric dipole moment function of ammonia [cf. V. Špirko, J. Mol. Spectrosc.74, 456-464 (1979)].