Purpose: This study was performed to analyze clinical features and use of renal replacement therapy (RRT) for children who visit the pediatric emergency department with benign acute childhood myositis (BACM) or rhabdomyolysis. Methods: We retrospectively reviewed medical records of 289 children who visited the emergency department with BACM or rhabdomyolysis from January 2013 through December 2022. Clinical features, laboratory and microbiological findings, and outcomes were compared between children with the two diagnoses. Subsequently, multivariable logistic regressions were performed to identify factors associated with applying RRT. Results: Of the 289 children, a total of 212 were analyzed, including 93 with BACM and 119 with rhabdomyolysis. Influenza (70 of the 145 children [48.3%]) was the most common cause, followed by exercise (36 of 212 [17.0%]). Compared with the children with BACM, those with rhabdomyolysis showed significantly higher frequencies of being boys and hematuria, and higher concentrations of hemoglobin, creatinine, creatine kinase, and myoglobin. Continuous venovenous hemofiltration, a modality of RRT, was applied to 8 children (6.7%) with rhabdomyolysis, of whom 1 died. Creatine kinase was independently associated with the application of RRT (adjusted odds ratio, 1.06; 95% confidence interval, 1.00-1.12; P = 0.036). Conclusion Rhabdomyolysis in children who require RRT may be associated with a higher concentration of creatine kinase.