This study aimed to determine the diagnostic performance of transabdominal pelvic ultrasonography and bone age in identifying the onset of puberty in girls at the Clínica Las Américas in Medellín, Colombia.We included girls aged ≤ 11 years referred to our clinic between March 2016 and March 2019 for signs of puberty. We compared the findings on pelvic and breast ultrasonography and bone age versus the baseline measurement of luteinizing hormone (LH) in serum, used as the reference standard for identifying the onset of puberty. We calculated the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and positive and negative likelihood ratios, analyzing subgroups of patients of different ages.We analyzed 43 patients. Ultrasound assessment of breast development had the highest sensitivity (94.1%) of all the imaging parameters evaluated, but its specificity was low. However, characteristics such as the length of the body of the uterus> 3.0cm and the presence of endometrial echoes were highly specific for identifying the onset of puberty, particularly in patients aged ≤ 8 years.Pelvic ultrasonography, ultrasonographic assessment of Tanner stage of breast development, and the evaluation of bone age are useful tools for the imaging confirmation of the onset of puberty. The results of this study support the use of these techniques in clinical practice in the workup for pubertal disorders in girls.Copyright © 2020 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.