Abstract: MUAC is used as an indicator for assessing acute undernutrition among children below five years of age. WHO child growth standards (2006) have given age related z-scores for both boys and girls for MUAC for identification of acute undernutrition among children below five years. A total of 4737 observations for MUAC had been made on 2305 children below 6 years of age living in an urban slum of Delhi in this cross-linked study. MUAC was measured using fibreglass tape sensitive to the nearest mm using standard technique. MUAC z-scores (MUACZ) were computed using WHO child growth standards and nutritional status was assessed. Median MUACZ for both boys and girls was much lower than median value of MUAC for boys and girls in WHO Child Growth Standards (2006). There was no significant difference in mean values of MUAC between the boys and girls upto 4 years of age. It was observed that 53.9% of the children (age-combined) were undernourished (below -2SD MUACZ), of which 11.2 % had severe acute malnutrition (below -3 SD MUACZ). The single cut-off point for MUAC <12.5 cm underestimated the prevalence of undernutrition was 32.6% among children in the study. This clearly indicated that MUAC-for-age using WHO Child Growth Standards would help in identifying the burden of acute undernutrition among underprivileged children.