The pair of galaxies NGC 4038/39 (Arp, 244) has been observed at Hα wavelength with a scanning Pérot-Fabry interferometer and an IPCS at the Cassegrain focus of the 3.6 m ESO telescope. Hα profiles were thus obtained inside 256 × 256 pixels (0.91″ × 0.91″ each), providing 5741 velocity points with an accuracy better than 16 km s-1, covering the central part of the merging system. The velocity field exhibits severe distortions, not surprising because of the strong interaction. Comparison of our data with recent CO data (Stanford et al., 1990) inside NGC 4039 show a fairly good agreement. The grand design of the velocity field of NGC 4038 more clearly reminds of a classical rotating disk. A rough estimate of the masses of the galaxies indicates that they are both around 1010 M⊙ within a radius of 40″. Comparison with the most recent model of the antennae (Barnes, 1988) shows a strong discrepancy, the observed radial velocity range being half the expected value and the nuclei velocities differing by only 30 km s-1 instead of the expected 300 km s-1.