Background: There are many treatments for idiopathic toe-walking, including casts with or without injection of botulinum toxin A. Combined treatment with casts and botulinum toxin A has become more common even though there have been few studies of its efficacy and safety problems. Our aims were to conduct a randomized controlled trial to test the hypotheses that combined treatment with casts and botulinum toxin A is more effective than casts alone in reducing toewalking by patients five to fifteen years of age, and that the treatment effect correlates with the extent of coexisting neuropsychiatric problems. Methods: All patients who had been consecutively admitted to the pediatric orthopaedics department of our institution because of idiopathic toe-walking between November 2005 and April 2010 were considered for inclusion in the study. Forty-seven children constituted the study population. The children were randomized to undergo four weeks of treatment with below-the-knee casts either as the sole intervention or to undergo the cast treatment one to two weeks after receiving injections of botulinum toxin A into the calves. Before treatment and three and twelve months after cast removal, all children underwent three-dimensional (3-D) gait analysis. The severity of the idiopathic toe-walking was classified on the basis of the gait analysis, and the parents rated the time that their child spent on his/her toes during barefoot walking. Passive hip, knee, and ankle motion as well as ankle dorsiflexor strength were measured. Before treatment, all children were evaluated with a screening questionnaire for neuropsychiatric problems. Results: No differences were found in any outcome parameter between the groups before treatment or at three or twelve months after cast removal. Several gait-analysis parameters, passive ankle motion, and ankle dorsiflexor strength were improved at both three and twelve months in both groups, even though many children still demonstrated some degree of toe-walking. The treatment outcomes were not correlated with coexisting neuropsychiatric problems. Conclusion: Adding botulinum toxin-A injections prior to cast treatment for idiopathic toe-walking does not improve the outcome of cast-only treatment. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.