The causes of therapist-patient sex are complex and multidetermined. Efforts to understand why psychotherapists transgress sexual boundaries are hampered by the lure of reductionism and oversimplification. Most of those who examine this issue would prefer to categorize all such therapists as "bad" and "corrupt" as a way of distancing themselves and disavowing any similarities between these therapists and themselves. The pathology of therapists who commit sexual boundary violations generally falls into four broad categories: (1) psychotic disorders, (2) predatory psychopathy and paraphilias, (3) lovesickness, and (4) masochistic surrender. Although a variety of individual psychodynamic factors are involved within each group, this classification is highly useful for informed treatment planning.