Purpose: The author modified the technique of Grice-Green, for managing flexible flat foot, with severe hindfoot valgus and possible dorsiflexion more than $15^{circ}$. The purpose of this study was to evaluate the efficacy and results of this modified technique. Material and Methods: Total of 6 patients, 11 cases of pes planovalgus were operatively managed with Modified Grice-Green procedure from Nov. 1996 to April 2002. Total 11 cases in 6 patients were managed; 9 cases in 5 males, 2 cases in one female. The average age of the patients were 7.3 years (5.1-13.3 years). Average follow up period was 3.9 years (1.2-6.7 years). Patients were evaluated preoperatively and at last follow up radiologically and clinically. Radiologic evaluation were done by measuring the talocalcaneal and talo-$1^{st}$ metatarsal angles with the anteroposterior view; and by measuring the talo-$1^{st}$ metatarsal angles with the lateral view. The clinical outcome were rated by subjective and objective improvement level. Results: On follow up, 9 cases were complete satisfied, 2 cases were satisfied with minor reservation and no case had major reservations or dissatisfaction. Objective results were rated as excellent in 9 cases, good in 2 cases. Average preoperative talo-calcaneal and talo-$1^{st}$ metatarsal angles on anteroposterior radiograms were $34.4^{circ}$ ($16-40^{circ}$) and $32^{circ}$ ($8-48^{circ}$) respectively; which postoperatively on last follow up were $20^{circ}$ ($3-37^{circ}$) and $15.6^{circ}$ ($3-34^{circ}$) respectively. Average Preoperative talo-$1^{st}$ metatarsal angle on lateral radiogram was $18.4^{circ}$ ($6-30^{circ}$); which postoperatively on last follow up was $6.7^{circ}$ ($-6-17^{circ}$). Conclusion: Modified Grice-Green operative procedure is effective and satisfactory procedure for planovalgus deformity in children. but for more accurate results, more patients and further follow up period are needed.