OBJECTIVE It has long been assumed that mandated reporting statutes regarding child abuse are self-explanatory and that broad consensus exists as to the meaning and proper application of reasonable suspicion. However, no systematic investigation has examined how mandated reporters interpret and apply the concept of reasonable suspicion. The purpose of this study was to identify Pennsylvania pediatricians' understanding and interpretation of reasonable suspicion in the context of mandated reporting of suspected child abuse. Methodology. An anonymous survey was sent (Spring 2004) to all members of the Pennsylvania chapter of the American Academy of Pediatrics (n = 2051). Participants were given several operational frameworks to elicit their understanding of the concept of reasonable suspicion, 2 of which are reported here. Respondents were asked to imagine that they had examined a child for an injury that may have been caused by abuse and that they had gathered as much information as they felt was possible. They then were asked to quantify (in 2 different ways) the degree of likelihood needed for suspicion of child abuse to rise to the level of reasonable suspicion. The physicians were asked to identify (using a differential-diagnosis framework) how high on a rank-order list "abuse" would have to be for it to rise to the level of reasonable suspicion (ie, first on the list, second, third, and so on, down to tenth). The second framework, estimated probability, used a visual analog scale of 0% to 100% to determine how likely suspected abuse would have to be for physicians for them to feel that they had reasonable suspicion. That is, would they need to feel that there was a 99% likelihood that abuse occurred before they felt that they had reasonable suspicion, a 1% likelihood, or something in between? In addition to standard demographic features, respondents were queried regarding their education on child abuse, education on reasonable suspicion, frequency of reporting child abuse, and (self-reported) expertise regarding child abuse. The main outcome measures were physician responses on the 2 scales for interpreting reasonable suspicion. RESULTS Pediatricians (n = 1249) completed the survey (61% response rate). Their mean age was 43 years; 55% were female; and 78% were white. Seventy-six percent were board certified, and 65% reported being in primary care. There were no remarkable differences in responses based on age, gender, expertise with child abuse, frequency of reporting child abuse, or practice type. The responses of pediatric residents were indistinguishable from experienced physicians, and the responses of primary care pediatricians were no different from pediatric subspecialists. Wide variation was found in the thresholds that pediatricians set for what constituted reasonable suspicion. On the differential-diagnosis scale (DDS), 12% of pediatricians responded that abuse would have to rank first or second on the DDS before the possibility rose to the level of reasonable suspicion, 41% indicated a rank of third or fourth, and 47% reported that a rank anywhere from fifth to as low as tenth still qualified as reasonable suspicion. On the estimated-probability scale (EPS), 35% of pediatricians responded that for reasonable suspicion to exist, the probability of abuse needed to be 10% to 35%. By contrast, 25% of respondents identified a 40% to 50% probability, 25% stipulated a 60% to 70% probability, and 15% required a probability of >or=75%. In comparing individual responses for the 2 scales (ie, paired comparisons between each pediatrician's DDS ranking and the estimated probability he or she identified), 85% were found to be internally inconsistent. To be logically consistent, any score >or=50% on the EPS would need to correspond to a DDS ranking of 1; an EPS score of >or=34% would need to correspond with a DDS ranking no lower than 2; an EPS score of >or=25% no lower than a DDS ranking of 3; and so on. What we found, however, was that pediatricians commonly indicated that reasonable suspicion required a 50% to 60% probability that abuse occurred, but at the same time, they responded that child abuse could rank as low as fourth or fifth on the DDS and still qualify as reasonable suspicion. CONCLUSIONS The majority of states use the term "suspicion" in their mandated reporting statutes, and according to legal experts, "reasonable suspicion" represents an accurate generalization of most mandated reporting thresholds. Our data show significant variability in how pediatricians interpret reasonable suspicion, with a range of responses so broad as to question the assumption that the threshold for mandated reporting is understood, interpreted, or applied in a coherent and consistent manner. If the variability described here proves generalizable, it will require rethinking what society can expect from mandated reporters and what sort of training will be necessary to warrant those expectations.