BACKGROUND Dental caries is a global public health problem, especially in children. Most caries in developing countries remains untreated. Only limited data are available on the clinical consequences of untreated dental caries because there is no measure to quantify the prevalence and severity of oral conditions resulting from untreated dental caries. OBJECTIVE To present a new index to evaluate the prevalence and severity of oral conditions resulting from untreated dental caries. To validate the index within the Philippines National Oral Health Survey, 2006. METHODS The PUFA index records the presence of severely decayed teeth with visible pulpal involvement (P/p), ulceration caused by dislocated tooth fragments (U/u), fistula (F/f) and abscess (A/a). RESULTS Good kappa values show the reliability of the index. The prevalence of PUFA/pufa >0 was 85% and 56% for 6- and 12-year-olds, respectively. The mean number of teeth affected (PUFA/pufa) was 3.5 and 1.2 for 6- and 12-year-olds, respectively. In 6- and 12-year-olds, 40% and 41% of decayed teeth had progressed to odontogenic infections. CONCLUSIONS The PUFA index complements classical caries indices with relevant information for epidemiologists and health care planners.