This study is concerned with three adjacent genes that show sex specific patterns of expression and are situated in the 89B region of the Drosophila melanogaster genome. The two outer genes of the group, ovary1 (ov1) and ovary2 (ov2), which are both transcribed in towards the central gene, show ovary specific and ovary enriched expression patterns respectively. Transcription of the central gene, testis1 (te1), can only be detected in the germ line of the testis. cDNAs corresponding to all three transcription units have been isolated and sequenced. The temporal and spatial distribution of these transcripts have been investigated through Northern blot analysis and RNA in situ hybridisation experiments to ovaries and testes, using fragments of the isolated cDNAs as probes. The cDNA corresponding to te1, te1.3, is 1.3 kb long, a similar length to the transcript detected on Northern blots. This transcript was detected in the testis germ line throughout the gonial divisions and up until individualisation, with low level expression in late larval and pupal stage testes. tel.3 encodes a putative 40.46 kD polypeptide that is predominantly hydrophilic. Neither the nucleic acid nor the polypeptide sequence showed similarity to sequences in the Genbank, EMBL, or Swissprot data bases. A 365 amino acid product of 38 kD has been expressed from a section of tel.3.