The texture of a copolyesteramide, Vectra® B950, has been studied by optical microscopy. At rest, the defects are typical of a biaxial nematic phase, but under the influence of a magnetic field or under shear, the nematic transforms into a uniaxial phase. The Freedericksz geometry yields aK1elastic constant of the order of 10−8N. The diffusivitiesKIII/nandKII/nare obtained by measuring the light intensity transmitted through a sample during shear start-up and relaxation, and from this we estimateKIII≅ 10−9N andKII≅ 10−10N. Since the biaxiality is small, these uniaxial constants adequately describe the phase at rest.