Background: Infertility is customarily defined as the inability to conceive after 1 year of regular unprotected intercourse. The Practice Committee of the American Society for Reproductive Medicine (ASRM) has published guidelines for a standard infertility evaluation. It includes a semen analysis, assessment of ovulation, a hysterosalpingogram, and, if indicated, tests for ovarian reserve and laparoscopy. The aim of this study was to compare the possible changes in uterine artery doppler indices after the use of pentoxifylline and low dose aspirin in patients with unexplained fertility. Methods: This prospective comparative clinical study was conducted on patients age between 20 and 35 years old, body mass index (BMI) from 18 – 25 kg/m2, with unexplained infertility. Patients were divided into two equal groups: low dose aspirin group and pentoxifylline group. All patients were subjected to personal, husband, sexual and menstrual history taking, clinical examination, routine infertility investigations [Husband semen analysis, Hormonal investigation (FSH, LH, midluteal progesterone, prolactin, TSH)], hysterosalpingogram, laparoscope and transvaginal ultrasound. Results: There was no significant difference between both groups regarding age, BMI, occupation, residency, parity, type/duration of infertility, menstrual regularity/amount, dysmenorrhea, sexual intercourse frequency, using of lubricant or vaginal douching. There was no significant difference between the studied groups regarding FSH, LH, TSH, basal uterine artery RI and PI and S/D ratio at one and three months. Conclusions: In women with unexplained infertility, there was no significant difference between the effect of pentoxifylline and low dose aspirin on the uterine artery blood flow or Doppler indices (RI, PI and S/D ratio).