Results indicated that the two major criteria for substantiating mothers for failure-to-protect from child sexual abuse--that the mother knew about the abuse and failed to act protectively--were evaluated and met in nearly every case that was substantiated. Every mother who was substantiated knew about the abuse prior to the investigation and 96.7 percent of these mothers failed to act protectively. These two criteria, however, were overlooked in some cases in which the mothers knew about the abuse but failed to consistently act protectively. In these overlooked cases, other evidence suggested that the child was not in imminent harm and investigator notes indicated that these mothers were consistently believing and supportive of their children and did not have other problems, such as drug or alcohol dependency. Finally, the 17 investigators that wrote reports included in this study applied the same criteria consistently to substantiate mothers. Researchers compared 31 mothers who were and 62 mothers who were not substantiated by CPS investigators in Iowa for failure-to-protect from child sexual abuse. The two groups of mothers were matched on demographic characteristics, family structure, employment, and receipt of government assistance. Data included the CPA investigation reports, which contained information about whether the mother believed the abuse occurred; how supportive the mother was of the child; the frequency, duration, and severity of abuse; and the mother’s capacity to protect. Also coded were the CPS investigator’s gender, years of experience at CPS, and years of experience conducting investigations. Coded investigation reports were analyzed using chi-square, t-tests, and logistic regression models. Future research should continue to probe investigation outcomes from child sex abuse investigations using additional explanatory variables. Tables, references