Sperm have been studied for their obvious role in fertilization and as a model system for cell-cell interactions and cell signaling. Despite its central and critical role in reproduction, we know surprisingly little about the overall molecular composition of sperm. Interest in sperm function has greatly intensified for two reasons: first, it is becoming increasingly apparent that human infertility can be traced to male factors, including alterations in sperm proteins, and second, there is increasing empirical evidence that sperm provide essential factors, both nucleic acid- and protein-based, to early zygote development possibly beyond their role in fertilization. At the molecular level, study of the sperm proteome has revealed a variety of genetic mechanisms involved in the organization and evolution of sperm form and function. These discoveries are being augmented and expanded by the application of proteomics that directly identifies protein constituents of sperm. In this article I argue that sperm are ideal candidate cell types for proteomic analyses and describe the current state of the field focussing on the recently described sperm proteome in the fruit fly Drosophila melanogaster.