Recent years have seen an increase in research activity surrounding diagnostic methods, particularly in the assessment of early caries lesions. The drive for this has come from two disparate directions. The first is from the dentifrice industry who are keen to develop techniques that would permit caries clinical trials (CCTs) to be reduced in duration and subject numbers to permit the investigation of novel new anti-caries actives. The second is from clinicians who, armed with the therapies to remineralise early lesions are now seeking methods to reliably detect such demineralised areas and implement true preventative dentistry. This review examines novel technologies and the research supporting their use. Techniques based on visual, optical, radiographic and some emerging technologies are discussed. Each have their benefits although systems based on the auto-fluorescence (such as QLF) of teeth and electrical resistance (such as ECM) seem to offer the most hope for achieving reliable, accurate detection of the earliest stages of enamel demineralisation.