The objective of the present work is to determine the association existing between body mass index (BMI) of father, mother, and son. A cross-sectional study was carried out, with 316 students aged four to six years old, together with their respective fathers and mothers, the final sample being composed by 948 subjects. To determine the association strength between BMI of parents and children, a simple linear regression was applied. The results indicate that, independently, there is a positive and significant association between the BMI of fathers ((a) over cap=.114, p=.041) and mothers ((a) over cap=.233, p=.002) with that of their children. It is concluded that there is a high number of fathers and mothers with high BMI values, which exerts a positive and significant relationship on their children, showing greater strength on the mothers' values.