PURPOSE: To compare power Doppler and conventional color Doppler ultrasound (US) in the detection of blood now in the normal pediatric testis and to assess the symmetry of blood flow and the spectral Doppler tracing waveforms in the normal pediatric testis. MATERIALS AND METHODS: Testicular blood flow was assessed prospectively in 68 testes in 34 boys (age range, 6 weeks to 13 years; mean age, 4.6 years) with both conventional color and power Doppler US. Intratesticular blood now was graded as follows: 0, no intratesticular flaw; 1, single intratesticular Doppler signal identified; and 2, multiple intratesticular Doppler signals identified. The symmetry of intratesticular now was assessed both subjectively and objectively by using the same grading system. Spectral Doppler tracings were obtained in 62 testes in 31 patients. RESULTS: Power Doppler US demonstrated intratesticular blood flow in 66 (97%) testes. Color Doppler US demonstrated intratesticular blood flow in 60 (88%) testes. Combined techniques depicted blood flow in all 68 (100%) testes. Testicular blood now was judged symmetric in all 34 (100%) patients with power Doppler US and in 31 (91%) patients with color Doppler US. Spectral Doppler tracings demonstrated absence of diastolic now in 20 (32%) of 62 testes. CONCLUSION: In children, power Doppler US is more sensitive than color Doppler US in the detection of intratesticular blood now. With power Doppler US, testicular blood now in healthy children is symmetric, underscoring that the asymptomatic testis can be used as a baseline for assessing flow in the symptomatic testis.