This study was carried out to determine the folate status of adolescent girls. Serum and red blood cell(RBC) folate levels of 132 Korean adolescent girls aged 12 to 15 years were evaluated by micorbioligical assay using Lactobacillus casei(ATCC 7469). Serum folate concentrations were less than 3ng/ml in 4.5% and 3 to 4.9ng/ml in 42.4%. Of the RBC folate values, 4.5% were less than 120ng/ml and 40.2% were 120 to 159ng/ml. These findings demonstrated that serum folate levels were subnormal in 46.9% and RBC folate levels were subnormal in 44.7% of the adolescent girls. Serum and RBC folate concentration tend to be high in folate supplemented subjects. There was no significant difference in serum and RBC folate levels, hemoglobin, and hematocrit values between regular meal group and irregular meal group.