Purpose: To evaluate the value and limitation of modified Mau osteotomy through the review of 30 feet treated by this procedure. Materials and Methods: We retrospectively analyzed 30 cases treated with modified Mau osteotomy since 2002. The mean duration of follow-up was 10 months. We reviewed medical records to describe each case and select several clinical factors which related with surgical procedure and could influence on final results. We measured radiographic parameters such as hallux valgus angle (HVA), intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA), sesamoid position and also assessed clinical outcomes by AOFAS score and satisfaction degrees. Results: The mean preoperative HVA and IMA were $40.4^{circ}$, $17.4^{circ}$ and the mean amounts of correction were $31.2^{circ}$ and $11.5^{circ}$. Amounts of delayed loss of correction were 16.8% in HVA and 19.2% in IMA. Initial HVA, rotational angle and translation distance of the distal fragment, stability of fixation, first ray instability were revealed as significant factors for the final result from this procedure. DMAA was increased by rotation of the distal fragment and decreased by adding translation on the rotation. Conclusion: Modified Mau osteotomy is an effective procedure to get enough correction. But, it is important to try to avoid excessive rotation of the distal fragment because it may worse joint congruity. It may be worthwhile to pay close attention to the direction of saw and stability of fixation.