For a long time, sex has been a topic of enormous interest among evolutionary biologists. What is the origin of sex? Why is that so many species have only two sexes? What is the origin of sex chromosomes? Why has the Y-chromosome evolved to retain only a few genes? What is the pattern of evolution among sex-linked genes? Why is it that so many genes linked to reproductive traits have rapidly evolved among closely related species? How have mutation, demographic factors, and selection contributed to the evolution of sex-related genes? These are only some of the many questions that have been pursued over the years making sex, sex-related traits, their genetics, and their evolution within the genome recurrent topics of inquiry.

Following the successful publication of our first issue on the evolution of sex-related traits and genes (http://www.hindawi.com/journals/ijeb/2011/si.estg/), we are pleased to announce the launching of an annual special focus issue on the topic. This issue will become the second in a series of special issues or focus issues to be published each year. We are now inviting authors to submit original research articles as well as review articles that will stimulate, contribute, and challenge our continuous effort to understand what drives the evolution of sex-related traits and genes. Potential topics include, but are not limited to:

• The evolution of mating behavior interactions
• Postmating challenges to fertilization and sexual selection
• The evolution of sex/gamete developmental pathways and genes
• Molecular evolution of reproductive genes and proteins
• Patterns of evolution within a genomic context
• Reproductive traits and speciation

Before submission authors should carefully read over the journal's Author Guidelines, which are located at http://www.hindawi.com/journals/ijeb/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/ according to the following timetable: