A quantum Hamiltonian describing N particles on a line interacting pairwise via an elliptic function potential in the presence of an external field is introduced. For a discrete set of values of the strength of the external potential, it is shown that a finite number of eigenfunctions and eigenvalues of the model can be exactly computed in an algebraic way. 2001 Elsevier Science B.V. All rights reserved. PACS: 03.65.Fd; 71.10.Pm; 11.10.Lm It is well known that the class of exactly solvable problems does not include most physical problems. The development of computer science in the last decades has made possible the use of numerical methods to approximate exact solutions in a wide variety of situations. Yet, the study of exactly solvable models still deserves attention, not only because the knowledge of exact solutions can be used to test approximate methods, but also in its own right, due to the simplicity and mathematical beauty of the models, and the wide range of connections with other fields of physical and mathematical research. This is illustrated by the renewed interest in the Calogero-Sutherland (CS) models of interacting particles in one dimension, which have been recently applied to many different fields such us quantum spin chains with long range interaction The first example of a non-trivial integrable quantum many-body problem was found by Calogero [8], and consists of a system of identical nonrelativistic particles interacting pairwise through an inverse-square potential v(r) = r −2 , so that the Hamiltonian is