Background: Impaired nutritional status is a major health problem affecting young children in developing countries that has a significant impact on child morbidity and mortality., Aims: This study aimed to assess the prevalence of undernutrition among children aged < 5 years, using conventional indices and the Composite Index of Anthropometric Failure (CIAF), and then comparing their estimated results., Methods: A community-based cross-sectional study was conducted and information was collected through house-tohouse visits using precoded structured records. We analysed data from 1292 children aged 6-59 months, from Ahwar and Al-Mahfed rural districts in Abyan Governate, South Yemen, with reference to the 2006 World Health Organization growth standards., Results: CIAF identified undernutrition in 70.1% of children, while conventional anthropometric indices revealed 38.5% stunting, 39.9% wasting, and 55.1% underweight. Compared with conventional indices, CIAF aggregate recognized 31.6%, 30.2% and 15% more undernourished children than stunting, wasting and underweight separately. According to CIAF, 21% had a single anthropometric failure and 49.2% exhibited multiple failures. Stunting Index, Wasting Index and Underweight Index were 0.55, 0.57 and 0.79, respectively., Conclusions: CIAF gives a better estimate of undernutrition than currently used conventional indices; identifies more children with multiple anthropometric failures; and reflects a wider view of the extent and pattern of undernutrition of children living in communities with limited resource settings., (Copyright © World Health Organization (WHO) 2018. Some rights reserved. This work is available under the CC BY-NC-SA 3.0 IGO license (https://creativecommons.org/licenses/by-nc-sa/3.0/igo).)