This study examined the outcomes of ultrasound-monitored Pavlik harness treatment in 25 infants (2 boys and 23 girls) representing a total of 31 cases of developmental dysplasia of the hip of Graf type IIc or more severe. For all infants, Pavlik harness treatment started after ultrasonographic diagnosis in our clinic. If there was no improvement by the third week of follow-up, the harness treatment was discontinued. Of the 25 patients (31 hips), 16 patients (18 hips) were successfully treated with the Pavlik harness. The effects of age at start of treatment, gender, side of pathology, first clinical evaluation findings, bilaterality, and Graf type on Pavlik harness treatment success were analysed. We found that the outcome of treatment with the Pavlik harness was related to Graf type, age at start of treatment, and bilaterality.