Objectives: To document uterine involution after vaginal delivery and cesarean section by abdominal sonography and to compare the efficacy of manual examination and ultrasonography. Study Design: Postpartum manual and sonographic assessment of uterine involution was performed in 120 patients following vaginal and cesarean delivery with an attempt to build a database of changes in uterine dimensions. The patients' reports on the intensity of uterine contractions and vaginal bleeding were compared to the results of sonographic imaging. Results: Palpation revealed proper uterine involution in 80 and 25% of patients after vaginal delivery and cesarean section, respectively. It could not be performed in 2.5% after vaginal delivery compared to 50% after cesarean section. Uterine length was found to be significantly greater after cesarean section than after vaginal delivery (p =0.0001), and the anterior uterine wall was significantly thinner than the posterior wall (p =0.0001). Uterine length was significantly greater in the presence of blood accumulation in the uterine cavity (20.7 cm), than when the uterus was empty (18.8 cm) (p =0.001). In correlating between the patient's report of intense bleeding and the sonographic picture of blood in the uterine cavity sonography had a sensitivity of 0.56 and a specificity of 0.83, whereas the patients' reports had a positive predictive value of 0.22. The difference in information provided by the patients versus that provided by sonography was highly significant (p =0.001, χ2 test). Conclusion: Within 3 days after delivery, patients particularly those having had a cesarean section, should undergo uterine sonographic scanning and manual palpation to evaluate involution and presence of blood in the uterine cavity.