OBJECTIVES: The goals were to determine how frequently primary care clinicians reported suspected physical child abuse, the levels of suspicion associated with reporting, and what factors influenced reporting to child protective services. METHODS: In this prospective observational study, 434 clinicians collected data on 15003 child injury visits, including information about the injury, child, family, likelihood that the injury was caused by child abuse (5-point scale), and whether the injury was reported to child protective services. Data on 327 clinicians indicating some suspicion of child abuse for 1683 injuries were analyzed. RESULTS: Clinicians reported 95 (6%) of the 1683 patients to child protective services. Clinicians did not report 27% of injuries considered likely or very likely caused by child abuse and 76% of injuries considered possibly caused by child abuse. Reporting rates were increased if the clinician perceived the injury to be inconsistent with the history and if the patient was referred to the clinician for suspected child abuse. Patients who had an injury that was not a laceration, who had >1 family risk factor, who had a serious injury, who had a child risk factor other than an inconsistent injury, who were black, or who were unfamiliar to the clinician were more likely to be reported. Clinicians who had not reported all suspicious injuries during their career or who had lost families as patients because of previous reports were more likely to report suspicious injuries. CONCLUSIONS: Clinicians had some degree of suspicion that approximately 10% of the injuries they evaluated were caused by child abuse. Clinicians did not report all suspicious injuries to child protective services, even if the level of suspicion was high (likely or very likely caused by child abuse). Child, family, and injury characteristics and clinician previous experiences influenced decisions to report.