The present invention relates to a method for obtaining a transgenic monocotyledon plant containing a gene of interest free of foreign ancillary sequences comprising: a) transforming at least one cell of a plant having no active transposase with a vector comprising two expression cassettes, one comprising a nucleotide sequence of interest (i), the other comprising a nucleotide sequence encoding a selection marker (ii) bordered by the mobilizable sequences of a transposon, said first expression cassette (comprising the nucleotide sequence of interest (i)) being outside the transposon element; b) selecting the transformed plants with the selection marker (ii); c) crossing a transformed plant with another plant belonging to a line containing in its genome a gene encoding an endogenous active transposase, and which is in the middle of a phenotypic marker for excision (iii), to obtain an F1 or any other individual of a subsequent generation; d) selecting the cells or the individuals carrying the gene of interest free of foreign ancillary sequence, from the F1 generation; e) regenerating plants from the cells or the individuals selected in (d).