An X-ray radial atomic distribution (RDF) study of the amorphous alloy As 0.20Se 0.40Te 0.40 was performed. Short-range order information was obtained by interpreting the RDF data using a theoretical expression which takes into account the variation of the atomic scattering factors with s, the scattering vector modulus. The existence of tetra- and tri-coordinated arsenic atoms, suggested in the literature for glassy alloys containing this element, was found to be compatible with the experimentally obtained structural information. A spatial atomic distribution model was generated according to these two possible coordinations for arsenic, using the conveniently modified Metropolis Monte Carlo method. The model obtained exhibits tetrahedral units on arsenic atoms, forming a network with triangular pyramids with an arsenic atom at some vertices. A comparative analysis of the parameters of this model showed good agreement with the values given in the literature for similar alloys.