In this cross-sectional study, 932 school boys and 927 school girls,6-10 years old of Khorramabad, Lorestan were selected randomly by proportionate multi-stage cluster sampling method. All students underwent clinical examination for presence of Goiter with the method and criteria recommended by world health organization ( WHO). Age specific prevalence rates of Goiter in boys 6 through 10 years, were 49.5-62.6-64-65.5 and 63.5 percent, and in girls were 70.6 -74 – 65.2- 70.4 and 80 percent respectively. Khorramabad is considered as a hyperenbemic area for Goiter. Comparison of prevalence rates in both sexes revealed that the rates were significantly higher in girls at all ages ( p<0.001). Also , total prevalence rates of Goiter in girls (72℅) and boys (61℅) were significantly different ( p<0.001). In different regions of the city the prevalence rates were more than 50℅ . Age specific prevalence rates in girls in groups of 6-8 years and 9-10 years and in boys in previous group were significantly different. Girl to boy sex ratio as an index of severity of endemia was 1.24 at age of 6 and 1.27 at age of 10. The results showed that the prevalence rates of Goiter in this area is significantly lower than the rate reported in 1989.