Abstract Child sex abuse increasingly is recognised as a societal problem that can no longer be ignored. In this paper definitions, prevalence, trends, assessment, and available diagnostic procedures are described and critically evaluated. It is argued that the lack of reliable diagnostic procedures remains one of the main difficulties in dealing effectively with the detrimental effects of CSA on the or adult. The research challenge to find effective alternative procedures is outlined. Key words: sex abuse (CSA), diagnosis, disclosure, assessment. Introduction Child Sex Abuse (CSA) is a social problem that demands vigorous scrutiny and formal investigation. Although some form of incest taboo has existed across most cultures, the sexual abuse of children has been denied, condoned, and sanctioned throughout history. Over the last decade research in the area of CSA has increased exponentially and has attracted increasing attention not only from health professionals (Miller & Veltkamp, 1995) but also from public, legal, and media interest. Issues surrounding CSA include the veracity of the reports, the extent of the short-term and long-term negative effects on the child, and the controversy over therapeutic interventions to help overcome the long-term negative effects of CSA. Sexual abuse of children includes many types of sexual trauma, from single attacks by strangers to long-term incestuous relationships with a parent or close relative. In this paper, the term sexual abuse will be used to denote all types of sexual victimization, whereas incest will be used only with respect to sexual experiences between individuals related by blood or by marriage, with whom such activity is prohibited by virtue of societal taboos. Problems with definitions Despite efforts to promote a uniform criterion for defining CSA, there are still variations in the definitions adopted by professionals and researchers working in the field. The definition of CSA varies on several dimensions, for example, the level of physical contact, the age of the victim, the age of the perpetrator, the age difference between the victim and the perpetrator, and issues to do with consent. Legally CSA may be defined as any activity, before the age of legal consent, for sexual gratification of an adult or significantly older child (Rappley & Woolford, 1998, p. 49), while most commonly CSA is defined as: ... the involvement of dependent and immature children or adolescents in sexual activities they do not fully understand and to which they are unable to give informed consent, and which violate social taboos of family roles. (Helfer & Kempe, 1976, p.60). By-and-large researchers agree that the definition of CSA should not be confined to actual physical violation of a by rape, as this will adversely affect reported cases. Importantly definitional differences can markedly affect prevalence rates (Haugaard & Emery, 1989; Russell, 1984; Wyatt, 1985; Wyatt & Peters 1986). In the Irish context, Ward (1997) extended the definition of sexual abuse to include exposure to pornography, sexual exhibitionism, perverse activities, and viewing of sexual acts. Also included is a range of sexual contact between adults and children from fondling, oral-genital contact, digital penetration, (all of which do not leave any physically detectable traces), to intercourse. Furthermore, it is widely agreed that any definition of CSA should include the use of power over the child, for example, threats and/or exploitation of relationships that include an authority differential or some kind of dependence, no matter what the age of the abuser or abused. Once all these factors are included in the definition a different picture of prevalence rates emerges. Prevalence Over the last two decades the United Kingdom and Ireland, like most other countries worldwide, have witnessed a substantial increase in the number of reported incidents of CSA (Benedeck & Schetky, 1987; Dammeyer, 1998; Haugaard & Emery, 1989; Lamb, 1994; Wood, Orsak, Murphy, Cross, 1996). …