BACKGROUND: In symptomatic neonates with tetralogy of Fallot with pulmonary stenosis (TOF/PS), limited contemporary data exist regarding the effect of a modified Blalock-Taussig shunt (mBTS) on pulmonary valve (PV) and pulmonary artery (PA) growth and on the incidence of PV preservation at the time of complete repair. METHODS: We retrospectively studied patients who underwent repair of TOF/PS from 2000 to 2012 at our center. In neonates with TOF/PS palliated with an mBTS, we assessed PV annulus, main PA (MPA), and branch PAs (left PA [LPA] and right PA [RPA]) size by echocardiography before mBTS and surgical repair. RESULTS: Of 172 patients with TOF/PS, 40 (23%) were palliated with an mBTS at a median age of 23 days, and 31 met criteria for echocardiographic analysis. Palliated patients had hypoplastic PV, MPA, RPA, and LPA at baseline. All structures had significant absolute growth before surgical repair (p < 0.001). PV and MPA Z scores were unchanged, whereas branch PAs showed significant improvement (RPA, p = 0.03; LPA, p = 0.008). A PV-sparing repair was performed in 116 of 132 primary repairs (88%) and in 10 of 31 palliated patients (32%). At a median follow-up of 4.0 years (range, 0.7 to 12.6 years), no palliated patients required reintervention for right ventricular outflow tract obstruction. CONCLUSIONS: Significant absolute growth of the PV, MPA, RPA, and LPA occurs after an mBTS in neonates with TOF/PS. Branch PA size normalizes before complete repair. In one-third of patients with hypoplastic PVs, absolute growth after an mBTS may have facilitated valve-sparing repair.