A method for the production of a recombinant parvoviral virion, which method comprises the steps of: (a) providing an insect cell comprising one or more nucleic acid constructs comprising: (i) a nucleotide sequence comprising a transgene that is flanked by at least one parvoviral inverted terminal repeat nucleotide sequence; (ii) a first expression cassette comprising a nucleotide sequence comprising a single open reading frame encoding a full-length parvoviral Rep78 protein from which both Rep52 and Rep78 proteins are expressed in the insect cell, which nucleotide sequence is operably linked to a first promoter that is capable of driving expression of Rep proteins in the insect cell, and wherein the nucleotide sequence encoding the parvoviral Rep78 protein does not comprise an artificial intron; (iii) a second expression cassette comprising a nucleotide sequence encoding a parvoviral capsid protein which is operably linked to a second promoter that is capable of driving expression of the capsid protein in the insect cell; and (b) culturing the cell defined in (a) under a condition conducive to the expression of the Rep and the capsid protein; wherein the first and second expression cassettes are present on a single nucleic acid construct, wherein the first and second expression cassettes are present in equimolar amount in the insect cell, and wherein the first promoter is equally strong as the second promoter. (a) providing an insect cell comprising one or more nucleic acid constructs comprising: (i) a nucleotide sequence comprising a transgene that is flanked by at least one parvoviral inverted terminal repeat nucleotide sequence; (ii) a first expression cassette comprising a nucleotide sequence comprising a single open reading frame encoding a full-length parvoviral Rep78 protein from which both Rep52 and Rep78 proteins are expressed in the insect cell, which nucleotide sequence is operably linked to a first promoter that is capable of driving expression of Rep proteins in the insect cell, and wherein the nucleotide sequence encoding the parvoviral Rep78 protein does not comprise an artificial intron; (iii) a second expression cassette comprising a nucleotide sequence encoding a parvoviral capsid protein which is operably linked to a second promoter that is capable of driving expression of the capsid protein in the insect cell; and (i) a nucleotide sequence comprising a transgene that is flanked by at least one parvoviral inverted terminal repeat nucleotide sequence; (ii) a first expression cassette comprising a nucleotide sequence comprising a single open reading frame encoding a full-length parvoviral Rep78 protein from which both Rep52 and Rep78 proteins are expressed in the insect cell, which nucleotide sequence is operably linked to a first promoter that is capable of driving expression of Rep proteins in the insect cell, and wherein the nucleotide sequence encoding the parvoviral Rep78 protein does not comprise an artificial intron; (iii) a second expression cassette comprising a nucleotide sequence encoding a parvoviral capsid protein which is operably linked to a second promoter that is capable of driving expression of the capsid protein in the insect cell; and (b) culturing the cell defined in (a) under a condition conducive to the expression of the Rep and the capsid protein;