Sexual selection, including sexual conflicts, should leave signatures of molecular coevolution across populations and species. Additionally, it predicts that there should be genotype by genotype interaction effects on interaction phenotypes, for example in outcomes of mating interactions. We will be testing these predictions using population genomic and genotyping data from Drosophila melanogaster. Publicly available data are available from DrosEU and the DGRP panel. We will use population genomic data from DrosEU to conduct custom co-evolutionary analyses across populations to test for a co-evolutionary signal. We can then associate these patterns to results from behavioural experiments in the lab. We will also be using DGRP data to test for associations between pairs of alleles at candidate genes and interaction phenotypes from controlled crosses of DGRP lines. These analses will address fundamental questions in sexual selection theory and evolutionary biology.