In many species, sperm and egg membranes fuse during fertilization to allow the parental genomes to combine. This membrane fusion requires exocytosis of the acrosome, an organelle located apical to the sperm nucleus. Drosophila sperm, however, enter eggs with their membranes intact and then undergo plasma membrane breakdown (PMBD). How this is accomplished has been a mystery, but on p. 4871 Wilson and coworkers report that Sneaky, a new acrosomal protein, is required for PMBD. The researchers show that the plasma membrane persists around sneaky mutant sperm after egg penetration, which results in male sterility. Using GFP-tagged Sneaky and an acrosomal marker,they demonstrate that normal sperm donate intact acrosomes to eggs. They propose, therefore, that the Drosophila acrosome acts as a signalling vesicle that elicits change in the overlying sperm plasma membrane, a novel role that requires Sneaky. If the human Sneaky-like proteins that have been identified are also required for sperm function, the researchers add, they may provide new targets for male contraceptives.