A 20-year review was conducted of children presenting with psoas abscess at two major pediatric hospitals. Eleven children with psoas abscesses were identified. The extreme variability in the clinical presentation of this condition is shown. Psoas abscess was most difficult to differentiate from septic arthritis of the hip in pediatric patients. This study also shows the often circuitous investigative route traversed before arriving at the diagnosis of psoas abscess. Atypical features, such as femoral nerve neurapraxia or bladder irritability in association with hip pain, should alert the clinician to consider psoas abscess. Based on this study, a diagnostic algorithm to differentiate between psoas abscess and septic hip was formulated.