The invention pertains to a method for selecting at least one eukaryotic host cell expressing a product of interest, comprising (a) providing a plurality of eukaryotic host cells, wherein cellular viability of said host cells is dependent upon folate uptake, wherein said host cells comprise at least (i) a foreign polynucleotide encoding a product of interest and (ii) a foreign polynucleotide encoding a DHFR enzyme; (b) culturing said plurality of eukaryotic host cells in a selective culture medium comprising at least an inhibitor of DHFR and folate in a limiting concentration; and (c) selecting at least one eukaryotic host cell expressing the product of interest. Also provided is a method for expressing a product of interest which is based on host cells selected by said method and a cell culture medium.