A repeated DNA sequence used for epidemiological studies of the human opportunistic pathogen Aspergillus fumigatus has been characterized. It is a retroelement of 6914 bp in length, bounded by long terminal repeats of 282 bp, with sequence and features characteristic of retroviruses and retrotransposons. A 5 bp duplication site was found at its borders. This element, designated Afut1, encodes amino acid sequences homologous to the reverse transcriptase, RNase H and endonuclease encoded by the pol genes of retroelements. Comparison of the peptidic sequences with other putative polypeptides of fungal LTR retrotransposons showed that Afut1 is a member of the gypsy group. This is the first report of a transposable element in A.fumigatus. Afut1 is a defective element: the putative coding domains contain multiple stop codons due exclusively to transitions from C:G to T:A.