A genomic library from the yeastPichia anomala has been constructed and employed to clone the gene encoding the sucrose-hydrolysing enzyme invertase by complementation of a sucrose non-fermenting mutant ofSaccharomyces cerevisiae. The cloned gene,INV1, was sequenced and found to encode a polypeptide of 550 amino acids which contained a 22 amino-acid signal sequence and ten potential glycosylation sites. The amino-acid sequence shows significant identity with other yeast invertases and also withKluyveromyces marxianus inulinase, a yeast -fructofuranosidase which has a different substrate specificity. The nucleotide sequences of the 5 and 3 non-coding regions were found to contain several consensus motifs probably involved in the initiation and termination of gene transcription.