Objective: This study aimed to summarize our experience with modified drilling epiphysiodesis and prediction methods for accurate timing of surgery and to compare the results with those of recent work by other authors. METHODS: The Macnicol and Gupta modified drilling technique was used. Distal femoral and/or proximal tibial permanent epiphysiodesis was performed in 42 children (21 boys, 21 girls; median age at surgery=12.6 years, age range=9.4-15.4 years) between 2004 and 2016. Based on the groundwork of previous studies, we developed an auxological prediction method. The limb length discrepancy (LLD) was assessed by clinical examination and verified by an x-ray of the hips when standing with blocks under the shorter leg. Results: The predicted shortening was 2.7 cm ± 1.1 cm. The final discrepancy after finishing skeletal growth was 0.5 ± 0.5 cm. In 26 patients (61.9%), equalization of both legs was achieved (0-0.5 cm). In 4 patients (9.5%), the remaining shortening was more than 1.0 cm. Shortening of an initially longer leg occurred in two patients (0.5 cm and 0.6 cm). Failure of growth plate arrest was observed in 1 patient. In another 3 patients, the efficacy of tibial epiphysiodesis was unsatisfactory. Minor complications occurred in 5 cases, but there was no evidence of angular deformity in the frontal and sagittal planes or proximal fibula overgrowth. Three patients (7.1%) returned to the operating room. Compared to published data, more patients achieved complete equalization of leg length. Conclusion: The results of this study verified the accuracy of the auxological prediction algorithm of LLD based on Shapiro’s findings. The surgical outcome is comparable between Shapiro patterns 1 and 3. Auxological examination, assessment of bone age, and sexual maturation are crucial tools for accurate timing of surgery.