A non-linear equation of the type log w - 0.008 h = a - be-kl for weight (w) and height (h) of 1177 infants and pre-school children from the Rural Health Centre area in Ballabhgarh was fitted by modified Guass-Newton Method using BMDP 03R program. On applying the non-linear model to the data of the present study it was found that the curve was a good fit in both sexes and also in all nutritional groups. The value of 'a' (the nutritional index) was almost the same in boys and girls but it was higher in case of children with normal nutrition (0.37) and lower in children with malnutrition (0.34 in Grade I, 0.32 in Grade II and 0.28 in Grades III & IV). The exponential term 'k' (index of maturation) was higher in boys compared to that of girls and higher in those with normal nutrition than with malnutrition. It was found that the rate of decay of the exponential term was slower in those with malnutrition compared to those with normal nutrition. While no difference was observed in the asymptotic value i.e., the rate at which infants reach the shape of older children, between boys and girls with normal nutrition (19 and 20 months respectively), it was delayed by 5 to 8 months in girls compared to boys with malnutrition. In the total sample, the Ehrenberg's index attained the asymptotic value at 20 months in boys and at 35 months in girls and at 27 months in the combined sample.