Composite membranes for nanofiltration were prepared by a polycondensation reaction between trimesoylchloride and different amines inside a dense layer of poly(ethylene oxide-b-amide). Use of amines containing ethylene glycol blocks resulted in membranes with best performance; hydrophilic membranes with a cut-off as low as 600 g mol(-1) and a reasonable water permeability, around 31 h(-1) m(-2) bar(-1) were produced.