The ade1 gene of the fission yeast Schizosaccharomyces pombe encodes a bifunctional polypeptide with glycinamide ribotide synthetase (GARSase) and aminoimidazole ribotide synthetase (AIRSase) enzyme activities. These enzyme activities carry out the 2nd and 5th steps, respectively, of the purine synthetic pathway. We report the cloning of the ade1 gene on a 4.4 kb Sau3A insert in the yeast shuttle vector pWH5. Integration of this genomic insert at or near the ade1 locus and its ability to complement, by transformation, three different types of ade1 mutants proved that it contains the ade1 chromosomal gene. Analysis of the nucleotide sequence of this insert revealed the presence of an uninterrupted open reading frame of 2,367 pb. This sequence, and the predicted 789 amino acid sequence encoded, both show a high degree of homology with the functionally equivalent ade5,7 gene sequence of Saccharomyces cerevisiae (approx. 60% overall in both cases) and Gart gene sequences of Drosophila melanogaster. The size of the ade1 RNA transcript is about 2.7 kb.