The largest group of transposable elements in Drosophila melanogaster, copia-like elements, share some important structural features with and are intimately related in evolution to vertebrate retroviruses. To further clarify the relationship between retroviruses and copia-like transposable elements, we set out to determine the complete nucleotide sequence of the genome of 17.6, which has long terminal repeats homologous in nucleotide sequence to those of avian leukaemia-sarcoma virus. We report here that 17.6 contains three long open reading frames comparable with gag, pol and env genes in retrovirus. At the level of amino acid sequence, the longest open reading frame of 17.6 includes a coding sequence similar to that for reverse transcriptase, suggesting a role for this enzyme in the life cycle of some Drosophila copia-like elements, analogous to the situation in retrovirus.