The study reviewed the records of 1,885 children under age 18 who were evaluated for possible sexual abuse. Multiple logistic regression was used to model the effects of a number of variables and their interactions concerning the child, perpetrator, and abuse, as they related to different types of penetration. Older children were more likely to report all types of penetration except for oral contact with the perpetrator's genitals. Assaults by strangers were more likely to result in penetration, as were abuse situations of longer duration. Ethnicity was an important explanatory variable for both vaginal and rectal penetration. Black girls were more likely to report vaginal penetration; whereas Mexican-American children were more likely to report rectal penetration. Gender was also an important determinant, with boys being significantly more likely to report rectal and oral penetration. The study shows that the child's gender, age, and ethnicity; the relationship to the perpetrator; and the duration of the abuse were all associated with the report of penetration in child sexual abuse. 1 table, 3 figures, and 15 references