The family systems analysis of child sexual abuse is limited in its focus on father-daughter incest, its distinction between the nature of intrafamilial and extrafamilial child sexual abuse, its indifference to offender individual characteristics, and its tendency to place moral responsibility for father-daughter incest on the mother. The proposed expanded model identifies four preconditions for both intrafamilial and extrafamilial child sexual abuse. (1) A potential offender must have some motivation to sexually abuse a child. (2) The potential offender must overcome internal inhibitions against acting on the motivation. (3) The potential offender must overcome external impediments to acting on the motivation. (4) The potential offender or some other factor must overcome the child's resistance to sexual abuse. This model incorporates and expands on most of the insights of the family systems approach while focusing more on dynamics within the offender and facilitating a more insightful assignment of moral responsibility for the abuse. 31 references.