Introduction & Objective: Obesity (a scaled weight-by-height index) charts of a cohort of 317 healthy infants and their parents living in Shiraz (Southern Iran) are presented.

Materials & Methods: An adjusted weight-for-height was used to develop power type obesity indices, I_p=W/H^p. Polynomial modelling was used by applying the HRY (Healy, Rasbash, Yang) nonparametric method to estimate age-related smoothed centiles of obesity.

Results: The optimal value of p was found to be 2.5 for infants and 1 for their parents. No more than cubic and quadratic polynomials were needed to fit obesity-for-age smoothly for infants and their parents respectively. Infant's obesity increases from birth to six months of age and decreases later on to the age of 21 months when it becomes stable. Infants obesity in age – dependent however, parents obesity is almost age – independent.

Conclusion: Using age – dependent obesity index (a scaled weight by height) is an appropriate one which explores the degree of fatness .A local standard for assessing obesity in clinical practice as well as community health programmes in Iran is of urgent need, which our data serve this purpose.