Background: Subclinical hypothyroidism (SCH) is a biochemical disease which is characterized by elevated serum levels of thyroid stimulating hormone (TSH) with normal thyroid hormone levels. In an attempt to correct the disease at its entry point, we wished to find out the incidence of subclinical hypothyroidism in female college students in Kumbakonam, a semiurban town of India. Methods: Around 260 female college students who had no history of thyroid disease were screened for thyroid dysfunction by a TSH assay. Results: The mean age ± standard deviation was 18.72 ± 2.27 years. The mean TSH value was 3.98 mIU/mL. The incidence of abnormally high TSH values was around 11.5%. The number of such cases was 30 with low T3 values in six students. One had a value of 150 with no symptoms. Another student had a value of 0.15 and her T3-T4 profile was normal. All students were asymptomatic. None of the students had goiter.Conclusions: In an unpublished but accepted study, we found an incidence of 3.5% in the school female children in the age group of 15–17. A sudden jump in the incidence is occurring in the age group of 18–22. This needs a workup of the causative factors and their possible correction.