Objective To evaluate the role of ultrasound and color Doppler analyses in improving the differential diagnosis of pubertal precocities. Methods Sixty-nine girls with premature (<8 years old) breast development and/or pubic hair growth underwent: auxological (height, weight, body mass index, skeletal maturation), hormonal (basal, gonadotropin releasing hormone (GnRH)-test, adrenocorticotropic hormone test), and sonographic (uterine and ovarian volume and endometrial echo) including color Doppler (uterine arteries) evaluations. Results The uterine size was greater in girls with a pubertal response to the GnRH test (Group II, n=16; 7.48±4.18 mL) than in those with a prepubertal response to the GnRH test (Group I, n=17; 3.02±1.36 mL; P=0.006), an isolated pubarche (Group III; n=20; 2.58±1.32 mL; P<0.001) or an isolated thelarche (Group IV, n=16; 1.82+/-1.07 mL; P<0.001). Endometrial echo was observed in 87.5%, 29.4% and 5% of girls, respectively, in Groups II, I and III. The Doppler analysis of the uterine arteries showed the lowest impedance to be in patients with a pubertal response to the GnRH test (Group II). Conclusions Sonograpbic and color Doppler parameters may improve the diagnosis of GnRH-dependent precocious puberty and may be useful to determine which girls need treatment. Copyright (C) 2003 ISUOG. Published by John Wiley & Sons, Ltd.