We describe new vectors suitable for P-element mediated germ line transformation of Drosophila melanogaster using passenger genes whose expression does not result in a readily detectable phenotypic change of the transformed flies. The P-element vectors contain the white gene fused to the heat shock protein 70 (hsp70) gene promoter. Expression of the white gene rescues the white phenotype of recipient flies partly or completely even without heat treatment. Transformed descendents of most founder animals (GO) fall into two classes which are distinguishable by their orange and red eye colours. The different levels of white expression are presumably due to position effects associated with different chromosomal sites of insertion. Doubling of the gene dose in orange eyed fly stocks results in an easily visible darkening of the eye colour. Consequently, the generation of homozygous transformants is easily possible by simple inbreeding due to the phenotypic distinction of homo- and heterozygous transformants. Cloning into these P-element vectors is facilitated by the presence of polylinkers with 8 and 12 unique restriction sites.