This study was randomized clinical trial that was no blind study.Aim of study is comparison of labor phases in painless delivery with epidural analgesia and Entonox administration. This study was conducted on 90 pregnant women referred to Taleghani Hospital in Arak, Iran. Inclusion criteria: primigravida women; singleton pregnancies; term pregnancy of 37 to 42 weeks; no medical diseases; cervical dilation of 3 to 4 centimeter.Exclusion criteria: multiparous; multiple pregnancy; Preterm labor; Post-term labor. The first group (n=30) received epidural analgesia with injection of 0.125 percent Marcaine and Fentanyl (5 micro gram). The second group (n=30) received general analgesia with Entonox gas. In this study, the third group consisted of 30 pregnant women who were considered as control subjects receiving no medication for labor pain relief.Fetal heart rate was controlled every 15 minutes, and the duration of each labor phase was accurately calculated in minutes. With regards to labor progress, cervical examination was performed every two hours until full dilation of the cervix. This process continued until the infant was born, and the delivery was complete. Finally, neonatal Apgar scores were recorded in prepared forms by residents of gynecology.Comparison of the study groups was performed in terms of the duration of the first and second phases of labor, frequency of cesarean delivery, neonatal Apgar scores, and prevalence of postoperative complications (e.g., headache, nausea, vomiting, and backache).