The structural and electrochemical behavior of o-(LixWO3H2O)-H-. has been studied for several electrochemical Li intercalation/deintercalation processes. Four intercalated phases called alpha, beta, gamma and delta, were distinguished by means of in situ X-ray diffraction (XRD) experiments. The modification in the distance between the tungsten layers represented by the cell lattice parameter b was found to reflect the structural changes induced by Li intercalation. Thus, we found that potential cycling over the alpha phase (till x = 0.35) does not lead to any major degradation of the structure whereas reducing further (WO3H2O)-H-. and reaching the beta, gamma or delta phase introduces irreversible damages. Furthermore, the alpha intercalation domain divides into three subphases called alpha(0), alpha(1) and alpha(2). From the less intercalated phase to the most intercalated one, the structure exhibits increasing higher symmetry. The unintercalated orthorhombic cell (alpha(0) phase) first changes into a quasi-quadratic one where a approximate to c not equal b/2 (alpha(1) phase) and finally to a quasi-quadratic one where a approximate to c approximate to b/2 (alpha(2) phase). The knowledge of this intercalation behavior is essential to improve the performance of a recently built (WO3H2O)-H-.-based variable infrared reflectance plastic device. (C) 2003 Elsevier B.V. All rights reserved.