Aim: Despite known risks of spinal manipulative therapy (SMT), current radiographic guidelines do not allow assessment of all potential contraindications to treatment. Congenital or developmental anomalies are often asymptomatic but can represent an important contraindication to SMT. Although congenital or developmental anomalies are thought to be quite rare, prevalence data could not be found for the majority of these anomalies within the literature. Therefore, this research aimed to determine the prevalence of various congenital and developmental anomalies within a chiropractic-patient population and hence assess the suitability of current x-ray guidelines for the chiropractic profession. Methods: A retrospective study was undertaken on 3519 spinal plain-film x-ray reports taken within the Macquarie University Chiropractic Outpatient Clinics from 2000 to 2005. The number of congenital or developmental anomalies that would contraindicate SMT, or change the treatment approach, were collated. Prevalences of each anomaly were calculated per spinal region. Total prevalence of all congenital anomalies per spinal region was also calculated. Results: 2814 cervical films, 695 thoracic films and 1052 lumbar films were assessed for anomalies. The total percentage of congenital or developmental anomalies potentially contraindicating SMT was 30% (cervical spine), 0.9% (thoracic spine) and 22.5% (lumbar spine). The most common anomalies found were posterior ponticles (21.3%), transitional lumbar vertebrae (16.6%), lumbar spondylolisthesis (8.3%) and cervical ribs (5.1%). Conclusion: The prevalence of clinically significant congenital and developmental anomalies in the cervical and lumbar spine is significantly high as to warrant closer inspection of the current x-ray guidelines. However, the effect that the majority of these anomalies have on treatment is controversial.