Reverse osmosis to concentrate the lisinopril after a low-pressure liquid chromatography was tested under various process conditions on a pilot-scale unit. It was found that the permeate flux 20-30 L/hm(2) can be kept over the whole concentration range with a feed pressure up to 35 bar and that fouling is negligible. The rejection of lisinopril is almost complete. These data were used for a conceptual design and installation of an industrial scale reverse osmosis unit with the membrane surface area 60 m(2) and capacity of 1.5 m(3)/h permeate. The capital cost estimate is significantly lower compared to a single-stage vacuum evaporator. The operating cost estimate for evaporation is roughly $6.8/kg lisinopril, while the estimated cost for concentration of lisinopril solution with reverse osmosis taking into account the theoretical energy consumption by pumps is $0.23-0.33/kg lisinopril. Cost calculated from actual plant data is even lower, $0.16/kg lisinopril. The validation results of the full-scale unit and its trouble-free operation prove that the decision for reverse osmosis is economically justified and that the scale-up was technically successful.