The handedness of gastropods is genetically determined. The freshwater gastropod Lymnaea stagnalis is a normally dextral species, but contains minor sinistral populations. The gene responsible for handedness determination in this species is predicted to function maternally and specifically in the dextral-ovipositing snail. In this study, we used differential screening and cDNA subtraction to isolate eight "dextral genes" that are specific to, or enriched in, the dextral-ovipositing strains of L. stagnalis. These genes were promising candidates for the handedness-determining gene. In order to determine whether the true handedness-determining gene was among them, we tested for genetic correlations between the level of expression of each dextral gene and the handedness phenotype, i.e., the chirality of the next generation offspring, by using a collection of backcross F2 progeny of F1 offspring from crosses between dextral and sinistral strains. Although the present study could not identify the handedness-determining molecules, this approach appears to be promising for the isolation of such developmentally important genes.