Hydroperoxide lyase (HPL), an enzyme of the lipoxygenase (LOX) pathway in plants, metabolizes fatty acid hydroperoxides. The resulting 6-carbon aldehydes and alcohols are responsible for the "green" flavours of fresh produce. Studying the role and properties of this enzyme is important because it has wide application in flavouring and perfume industries. To investigate the activity and role of HPL, our laboratory identified an HPL gene from Arabidopsis thaliana. This gene was expressed using E. coli, and the enzyme activity was investigated using a spectrophotometric assay. Subsequently, degenerate primers were designed in order to identify tomato HPL using polymerase chain reaction techniques. A partial sequence of a tomato HPL gene was isolated, and the expression pattern of this tomato HPL gene was investigated. This work therefore represents a further step in the understanding of the LOX pathway and its enzymes, and includes the addition of two gene sequences to the HPL gene family.