Study objective: The aim of this study is to compare plasma remifentanil concentrations and pulmonary function tests in subjects receiving remifentanil infusion (RI) versus RI with paracervical block (PCB) during transvaginal ultrasound-guided oocyte retrieval (TUGOR).Design: Prospective, randomized.Setting: Assisted Conception Unit.Patients: Forty American Society of Anesthesiologists I subjects requiring TUGOR.Intervention: After ovarian hyperstimulation, subjects were randomly allocated into two groups to receive either RI (Group RI, n = 20) or RI with PCB (Group RI + PCB, n = 20).Measurements: Heart rate (HR), mean arterial pressure (MAP), peripheral oxygen saturation (SpO2), end tidal carbon dioxide (ETCO2) tension, forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC), and amount of remifentanil used were collected. Plasma remifentanil concentrations were calculated with STANPUMP software.Main results: HR, MAP, ETCO2, SpO2, FEV1, and FVC did not differ between the groups. Total amount of remifentanil used were 486 ± 1.81 μg and 321 ± 0.87 μg in groups RI and RI + PCB, respectively, (p < 0.05). In Group RI, plasma remifentanil concentrations were 4.7 ng mL−1 and 4.2 ng mL−1 during the second transvaginal puncture, and at the end of TUGOR, respectively, whereas corresponding plasma remifentanil concentrations were 3.1 ng mL−1 and 2.6 ng mL−1in Group RI + PCB (p < 0.05).Conclusion: Both anesthesia regimens provided satisfactory analgesia without affecting FEV1 and FVC, but significantly higher plasma remifentanil concentrations were calculated when only RI was used as an anesthetic technique.