Hepatitis A is a common disease in Ahwaz and it seems that most of children have immunity against this disease. At the present time, human gamma globulin is recommended for post-exposure prophylaxis. The aim of this study was to determine the immunity status of children against hepatitis A and need for post-exposure prophylaxis. For this purpose, during a period of 5 months, sera anti-HAV antibody levels were measuned in 800 (357 males and 443 females) students, aged 10-15 from four educational districts of Ahwaz city, using ELISA method. The results showed that 81.2% of children were seropositive and 18.8% were seronegative. The lowest rate of positive cases was in the forth district. The most positive cases were in low socio-economical class and the least positive cases were in high socio-economical class. Since more than 80% of cases were seropositive, therefore, if personal hygiene, specially hand washing, is practiced routinely, post-exposure prophylaxis may not be necessary and prophylactic gamma globulin injection is only advised for those cases who do not practice this habit routinely.