The recent commercialisation of nanofiltration membranes resistant toward organic solvents is a real opportunity for fine chemistry. This study deals with different ways of integration of organic solvent nanofiltration for a specific type of reactions known as olefin metathesis and shows the use of two nanofiltration membrane reactors both running in cross-flow filtration mode (0.1 m s(-1)). They are used either in semi-continuous or continuous mode. A model ring closing metathesis reaction is chosen for the demonstration. A commercially available pre-catalyst, namely Grubbs-Hoveyda II, as well as a commercial polyimide membrane (Starmem 122, MWCO 220 g mol(-1)) are used. Firstly, nanofiltration of the single pre-catalyst allows establishing that the highest retention is obtained with a 40 bar pressure. Secondly, this pressure is used with the two membrane reactors before testing other conditions. Finally, interests and limitations of the two reactors are discussed. (c) 2013 Elsevier B.V. All rights reserved.