Finkelhor's precondition model (1984) is proposed as a useful theoretical base. The precondition model is evaluated in terms of research published since 1984. Strategies for prevention, based on the four preconditions, are outlined. Some limitations of the model are discussed, and the need to integrate it with mainstream psychological theory is emphasized. Finkelhor's aim was to produce a model that would address both the intra-perpetrator and situational aspects of child sexual abuse and that is equally applicable to familial and nonfamilial incidents. His model amounts to the proposition that four preconditions must be met before sexual abuse can occur. Thus, it is a theory about the necessary conditions for abuse. The four preconditions are motivation to sexually abuse, overcoming internal inhibitors, overcoming external inhibitors, and overcoming the resistance of the child. The precondition model directs the clinician's attention to an important class of assessment and therapeutic targets. A comprehensive assessment and formulation must address the four preconditions. Examples of therapeutic methods that may be relevant to each precondition are shown in a table. Regarding motivation to sexually abuse, the preventive methods address emotional congruence, sexual arousal, and blockage. Methods to address internal inhibitors include alcohol education, cognitive therapy, pharmacology, general stress reduction, impulse control training, empathy training, and relapse prevention methods. Methods that address external inhibitors focus on family interventions, parent and carer education, child education, and increased/improved supervision. Methods that focus on child resistance involve child education and assertiveness training for children. 75 references