Background: Slipped Capital Femoral Epiphysis (SCFE) is the most common hip disorder among adolescents. A controversial subset of SCFE patients are those who experience a unilateral slip, followed by a slip on the opposite hip, known as a 'contralateral' slip. To prevent the development of a contralateral slip, some physicians prophylactically pin the unaffected hip of patients they suspect may eventually develop a contralateral SCFE. However, there is no definitive protocol with which to predict if a child will develop a contralateral slip. The goal of this retrospective study was to develop a clinical tool to assist physicians and patients in deciding whether or not to perform prophylactic contralateral hip pinning after first diagnosis of SCFE. Methods: A retrospective medical record review was conducted to gather information about patients who were treated for SCFE at the Rady Children's Hopsital, San Diego, between 1997 and 2009. Demographic information was collected from all participants who were treated for SCFE and only patients with two or more years of post-operative care were included in the study. Results: A total of 299 participants were included in the study, of whom 162 (54%) had a unilateral SCFE, 39 (13%) presented with an initial unilateral slip and further developed a contralateral SCFE, 47 (16%) had a unilateral SCFE and underwent prophylactic pinning for the unaffected hip, and 51(17%) had simultaneous bilateral slips. A sub-analysis was performed with the 201 patients who had unilateral involvement. After simultaneous adjustment for age, endocrine condition, and slip type, the following associations were observed: increasing age was found to be protective of contralateral SCFE (OR=0.72, 95% CI 0.56-0.93), presence of underlying endocrine condition was associated with an increase in contralateral SCFE (OR=3.94, 95% CI 1.02-15.21) and acute on chronic slips had higher odds of contralateral SCFE development than acute or chronic slips (OR=2.98, 95% CI 1.14-7.77). Conclusions: Results from this study can be incorporated into the clinical arena to use as a tool for assisting physicians in determining whether or not to prophylactically pin a patient with a unilateral SCFE. For clinical decision making, this model should not be used as an independent assessment tool; rather, it should be considered as a reference to consult in conjunction with the other published studies and decision models.