Background: Determination of the prevalence of diseases is an important step in health programs. Objective: To determine the prevalence of skin diseases in primary school students in Ahwaz. Patients and Methods: This cross-sectional study was done in March and April 1995 (Esfand 1373, Farvardin 1374) in Ahwaz. 3000 male and 3000 female primary school students were examined for the presence of skin disease by a physician. This sample comprised 5 percent of total primary school students of Ahwaz. Diagnosis was made on clinical findings, laboratory examinations and skin biopsy, if needed. Results: The most common skin diseases were: pityriasis alba, acne, freckle, keratosis pilaris, pediculosis capitis, chicken pox, wart, impetigo, herpes simplex and leishmaniasis. The most common diseases in girl were acne and pediculosis capitis and in boys were acne and warts. Also the prevalence of diseases was related to the economic status of students. Conclusion: Skin diseases are common in primary school students in Ahwaz. The prevalence of certain skin diseases was related to the sex and economic status of the students.