Sexual dysfunctions have a high prevalence in males and females, and an increase in research into its backgrounds, causes and treatment is clearly visible. Characterization of sexual dysfunctions is complex and often needs extensive clinical, psychological and psychiatric expertise to arrive at reliable diagnoses. The present volume illustrates various aspects involved in sexual (dys)functioning but also the complexity of the field. Premature ejaculation, erectile dysfunction, female interest/arousal disorder, hypogonadism, sexual side effects of antidepressants and circumcision are subject of the various contributions. The topics treated nicely illustrate the problems associated with sexual function and dysfunction, including lifestyle, biological, mental, sociocultural and religious aspects. The topics in this volume clearly demonstrate the importance of research on sexual functions and dysfunctions.