The structure of Nasicon-type copper(I) titanium phosphate CuTi2(PO4)3 has been investigated by neutron diffraction. The copper environment is a compromise between the usual linear coordination of copper(I) and the octahedral surrounding of the M(1) site within the 3-D [Ti2(PO4)3] skeleton. Preliminary results concerning the various mechanisms able to lead to the redox reaction Cu2++e-&rarrCu+ are reported.