Identification of genes explaining variation in quantitative traits or genetic risk factors of human diseases requires both good phenotypic- and genotypic data, but also efficient statistical methods. Genome-wide association studies may reveal association between phenotypic variation and variation at nucleotide level, thus potentially identify genetic variants. However, testing million of polymorphic nucleotide positions requires conservative correction for multiple testing which lowers the probability of finding genes with small to moderate effects. To alleviate this, we apply a gene based association approach grouping variants accordingly to gene position, thus lowering the number of statistical tests performed and increasing the probability of identifying genes with small to moderate effects. Using this approach we identify numerous genes associated with different types of stresses in Drosophila melanogaster, but also identify common genes that affects the stress traits.