Objective: To study the serum levels and correlation of vascular endothelial growth factor (VEGF), insulin-like growth factor 1 (IGF-1), hormonal profile, and Doppler blood flow changes within the ovarian stroma before and after laparoscopic ovarian drilling (LOD) in women with clomiphene-resistant polycystic ovary syndrome (PCOS). Design: Prospective controlled study. Setting: University teaching hospital. Patient(s): Twenty-five women with clomiphene-resistant PCOS (group 1) and 20 women with regular menstrual cycles as a comparison group (group 2). Intervention(s): Laparoscopic ovarian drilling. Main Outcome Measure(s): Serum levels of VEGF, IGF-1, and Doppler indices of ovarian stromal blood flow. Result(s): The serum levels of VEGF, IGF-1, T, and LH were significantly higher in group 1 before LOD than in group 2. The Doppler indices (pulsatility index and resistance index) of ovarian stromal blood flow were also significantly lower in group 1 before LOD than in group 2. The serum levels of VEGF, T, and LH were significantly reduced in group 1 after LOD compared with in group 1 before LOD. Doppler indices (pulsatility index and resistance index) of ovarian stromal blood flow were significantly increased after LOD. The VEGF levels before LOD were positively correlated with IGF-1, LH, and T. After LOD, the VEGF levels were positively correlated with LH and T. Conclusion(s): Higher serum levels of VEGF and IGF-1 may explain the increased vascularity that was demonstrated by Doppler blood flow measurements in PCOS. Laparoscopic ovarian drilling reduced serum VEGF, IGF-1, T, and LH and reduced ovarian blood flow velocities, which may explain the reduction of ovarian hyperstimulation syndrome in women with PCOS after LOD. (C) 2003 by American Society for Reproductive Medicine.