ADVANCES in the field of optical computing(1-3) will require the development of materials that combine a large nonlinear optical response with a fast response time. For many applications, this translates into a third-order nonlinear optical susceptibility, chi((3)), in excess of 10(-8) e.s.u., and a response time faster than 10 ps (ref. 4). Although a wide range of inorganic and organic(19-21) materials have been found to exhibit a large chi((3)) either the response times tend to be far too slow or the materials are not sufficiently stable for device applications. Recently, the transition-metal oxide Fe2O3 was found to have a large chi((3)) (ref. 22). Here we show that oxides of several other 3d transition metals show a similarly large nonlinear optical response; moreover, we find that a significant contribution to the overall chi((3)) (similar to 10(-8) e.s.u. in the case of V2O5) has a response time of the order of 35 ps.