This study was performed to identify the nutritional status and eating behaviors of underweight adolescent females aged 15 to 19 years. The subjects were selected using data from 2001 NHANS of Korea, and included 28 underweight and 160 normal-weight subjects. We found that the underweight group had significantly lower weight (9.8 kg), waist (6.9 cm), and hip circumference (7.2 cm) values than the normal-weight group; however height and waist-hip ratio were not different. Serum indices were within normal ranges and showed no differences between the two groups. The energy and nutrient intakes of most of the subjects were considered poor. For intake levels, the proportion of subjects below the EAR, NAR and INQ of each nutrient were also not significantly different between the groups. There were no differences in frequency for skipping meals, snacking, and eating-out between the groups. When comparing food frequency data for 62 food items, the underweight group consumed significantly more often of eggs, dried anchovies, mackerel, shellfish, and mushrooms than the normal-weight group. The former also had significantly less excercise/walking, more diet-control, and more rest/sleep than the latter. Subjects in both of two groups perceived their body images as over weight, so they practiced diet-control to reduce body weight, which is considered harmful as a healthy weight. In conclusion, the underweight group showed no differences in items of biochemical indices, nutrient intakes, and many dietary behaviors, but subjects revealed significantly higher food intake frequencies for several protein foods, as well as less excercise/walking, and more rest/sleep than the normal-weight group.