The vanadosilicate zeolite AM-6 is shown by a combination of spectroscopic techniques (UV-vis, Raman, XPS, XAS and EPR) to contain linear chains of alternating V=O and V-O bonds. The V(IV) ions in these chains are ferromagnetically coupled, and an excellent fit a to the susceptibility data with a one-dimensional Heisenberg model is obtained with J = 0.66(1) cm(-1). AM-6 is thus the first reported example of a microporous material incorporating one-dimensional ferromagnetic chains.