Congenital Talipes Equinovarus (CTEV) occurs in approximately 1 in 1000 live births. Most cases occur as an isolated birth defect and are considered idiopathic. The widespread adoption of the Ponseti technique of serial casting followed by Achilles tenotomy and long term bracing has revolutionised the outcomes in CTEV. In most cases, plantigrade, flexible, pain-free feet may be produced without the need for extensive surgery. It is estimated that about 10% of cases of CTEV are not idiopathic. These feet are stiffer and more challenging to treat. In particular, there is little evidence in the literature concerning the efficacy of the Ponseti method in these cases. In our institution, a dedicated weekly Ponseti clinic has operated since 2005. To date 140 patients have been treated. We prospectively enter all details regarding their management onto an independent international database. The aim of this study was to audit the non-idiopathic cases of CTEV and to assess the effectiveness of the Ponseti technique in these challenging cases. Outcome measures included the Pirani score and eventual need for surgical intervention. We identified 29 cases (46 feet) with non-idiopathic CTEV. This comprises 21% of our workload. Seventeen were bilateral. The commonest diagnoses were neuromuscular conditions such as spina bifida (5 cases) and cerebral palsy (3 cases). There were 4 cases of Trisomy 21. Other causes included Nail Patella syndrome, Moebius syndrome, Larsen syndrome and Ito syndrome. In approximately 12% of cases, the underlying disorder remained undiagnosed despite thorough medical and genetic testing. In cases of non-idiopathic CTEV, the mean starting Pirani score was 5.5 (out of 6). After serial casting and Achilles tenotomy, the average score was 2.0. Twenty-one of 46 feet (46%) ultimately required further surgical intervention (mostly posteromedial release). We found that certain conditions were more likely to be successfully treated with the Ponseti method – these included conditions characterised by ligamentous laxity such as Trisomy 21 and Ehlers Danlos syndrome. All patients showed some improvement in Pirani score after serial casting. We believe that it is essential to attempt the Ponseti method of serial casting in all cases of CTEV. More than half of all non-idiopathic cases will not require further surgical intervention – and those that do are not as stiff thanks to the effects of serial casting. Thus, the surgery required is not as complex as it might otherwise have been. This is the largest series of its kind in the current medical literature