We have constructed and tested several new vectors for P element-mediated gene transfer. These vectors contain restriction sites for cloning a wide variety of DNA fragments within a small, non-autonomous P element and can be used to efficiently transduce microinjected DNA sequences into the germ line chromosomes of D. melanogaster. The P element in one vector also carries the rosy gene which serves as an easily scored marker to facilitate the transfer of DNA fragments that do not themselves confer a recognizable phenotype. The failure of certain P element constructs to function as vectors suggests that P element sequences, in addition to the 31 bp inverse terminal repeats, are required in cis for transposition. Moreover, removal of the first 38 bp of the autonomous 2.9 kb P element appears to destroy its ability to provide a trans-acting factor (s) required for the transposition of non-autonomous P elements. Finally, we describe a genomic sequence arrangement that apparently arose by the transposition of a 54 kb composite P element from a tetramer plasmid.