Objective: To compare stromal echogenicity in women with clomiphene citrate (CC)-sensitive and CC-resistant polycystic ovary syndrome (PCOS), and to compare stromal echogenicity before and after laparoscopic ovarian drilling in women with CC-resistant PCOS. Design: Prospective study. Setting: University teaching hospital. Patient(s): Twenty-two infertile women. Intervention(s): Transvaginal ultrasound examination and laparoscopic ovarian drilling. Main Outcome Measure(s): Ovarian stromal index (ratio of mean ovarian stromal echogenicity to mean echogenicity of the entire ovary). Result(s): The mean (+/-SD) ovarian stromal index was 1.26 +/- 0.27 in the women with CC-sensitive PCOS and 1.22 +/- 0.11 in the women with CC-resistant PCOS. The ovarian stromal index and ovarian volume of the women with CC-resistant PCOS before and after ovarian drilling were not significantly different, Conclusion(s): There was no difference in the stromal index and ovarian volume between women with CC-sensitive PCOS and women with CC-resistant PCOS. There was no overall difference in the stromal index and ovarian volume in women with CC-resistant PCOS before and after ovarian drilling. (C) 1999 by American Society for Reproductive Medicine.