Ejaculation and orgasm usually occur simultaneously in men even though ejaculation and orgasm are two separate phenomenona. Ejaculation occurs in the genital organs, whereas orgasmic sensations, being related to the genitals, are mainly a cerebral event which involves the whole body. In a few clinical syndromes, orgasm or ejaculation appears to exist independent of each other. For example, men with anesthetic ejaculation experience a normal ejaculation, but suffer from an absence of orgasmic sensation. On the other hand, men with premature ejaculation suffer from a disturbed speed of ejaculation, but do have intact orgasmic sensation.

It is very unfortunate that a clear distinction between orgasm and ejaculation has not been made in DSM-IV (American Psychiatric Association, 1994). In DSM-IV, ejaculation disorders are categorized under the heading of Orgasmic Disorders. Strangely, in DSM-IV retarded ejaculation has been called "male orgasmic disorder," analogous to "female orgasmic disorder," whereas premature ejaculation has not been called premature orgasm. Moreover, two rather rare syndromes, anesthetic ejaculation as well as partial ejaculatory incompetence, have not been mentioned at all in DSM-IV.

The synonymous terminology of ejaculation and orgasm in DSM-IV is not in line with current neurobiological thinking. In recent years, much has become known about the neurobiology and neuropharmacology of ejaculation. From a neurobiological perspective, it seems likely that orgasm and ejaculation are mediated by different neural circuits and various neurotransmitter systems.

In last century, ejaculatory disorders have been approached mainly from a psychological perspective. Although neuroscientists over the last 30 years have gained clear evidence of the important role of the central nervous system in ejaculation, it is only in the last decade that clinicians have begun to accept that ejaculatory disturbances are neurobiologically determined and can be treated by medication. However, in contrast with what is known about ejaculation, there is still limited information about the neurobiology of orgasm.

The history of ejaculatory and orgasm disturbances is colored with much speculations and particularly with a dramatic absence of evidence-based research. For example, many sexologists still believe in or favor one of the many psychological etiologies that have been put forward for the different ejaculatory disturbances. However, not one of these psychological hypotheses and associated treatments has been thoroughly investigated according to evidencebased medical principles. Most of these studies are characterized by very weak methodologies and designs.

I myself am convinced that evidence-based medical research is the only way to understand and investigate the efficacy of both drug- and psychological treatment of ejaculatory disturbances. Thus, I have written this chapter with a focus on methodology and design. Today, a clinical understanding of male ejaculatory and orgasm disturbances is no longer possible without a basic understanding of the neurophysiology, neuropharmacology, and neuroanatomy of serotonergic neurons in the brain. Therefore, I will start off by giving you a general explanation and overview of serotonergic neurotransmission, serotonergic receptors and how animal sexual behavior determines our understanding of sexual psychopharmacology. After this basic pharmacological introduction, I will describe the ejaculatory disturbances in rank order of frequency in the general population. As most research in recent years has been focused on premature ejaculation, it is inevitable that this disorder receives more attention than the other ejaculatory disorders.