Abstract: The invention relates to polysulphone/polyether block copolycondensates having the recurring structural unit as in formula (I)--(--O--E--O--Ar.sup.1 --SO.sub.2 --Ar.sup.2 --)--W-- (I)whereinE is a divalent diphenolate radical andW is a polyether, polythioether or polyacetal possessing at least two hydroxyl groups and having an average molecular weight (M.sub.n) of from 400 to 30,000 andwherein the proportion of the radical W in the total polymer amounts to 5 to 99 wt. %,the preparation and use thereof for the production of moulded shapes, for example, membranes or catheter tubes.