An acid invertase (EC 3.2.1.26.) cDNA clone, CaAIV-18, was isolated form the red pericarp cDNA library of the hot pepepr (Capsicum annum L.) fruit. The CaAIV-18 clone has 2223 nucleotides and one open reading frame encoding 641 amino acid residues. Analysis of deduced amino acid sequences reveals that CaAIV-18 has a 24-amino acid transmembrane ancorregiion in its N-terminal, implying acid invertase in hot pepper may be localized in the membrane and not in the cytosol. This clone showed high homology to tomato acid invertase, Aiv1, in nucleotide and decuded amino acid sequences. In the Southern blot analysis, this clone proved to exist as single or low copy numbers on the genome of hot pepper. The clones had two well-conserved regions which appears in acid invertase of other plant species (eg. tomato, Arabidopsis, etc.) and yeasts. During fruit development, CaAIV-18 was expressed preferentially inthe ripe red stage.