Introduction. Circumferential periosteal release is a rarely reported procedure for paediatric limb lengthening. The technique involves circumferential excision of a strip of periosteum from the metaphysis of the distal femur, tibia and fibula. This study aims to determine the mid to long-term effectiveness of this technique. Materials and Methods. A retrospective case series was performed of all patients undergoing circumferential periosteal release of the distal femur and/or tibia between 2006 and 2017. Data collected included demographics, surgical indication, post-operative limb-lengths and complications. Data collection was stopped if a further procedure was performed that may affect limb-length (except a further release). Leg-length discrepancies were calculated as absolute values and as percentages of the longer limb-length. Final absolute and percentage discrepancies were compared to initial discrepancies using a paired t-test. Results. Eighteen patients (11 males) were identified, who underwent 25 procedures. The mean age at first surgery was 5.83 (SD 3.49). The commonest indication was congenital limb deficiency (13 patients). In 23 procedures the periosteum was released in two limb segments (distal femur and distal tibia), whereas in two patients it was released in a single limb segment. Five patients underwent repeat periosteal release, and one patient had three periosteal releases. Mean follow-up was 63.1 months (SD 33.9). Fifteen patients had sufficient data for statistical analysis. The mean initial absolute discrepancy was 2.01cm (SD 1.13), and the mean initial percentage discrepancy was 4.09% (SD 2.76). The mean final absolute discrepancy was 1.00cm (SD 1.62), and the mean percentage final discrepancy was 1.37% (SD 2.42). The mean reduction in absolute discrepancy was 0.52 cm (95%CI −0.04–1.08; p=0.068, paired t-test), and the mean reduction in percentage discrepancy was 2.00% (95% CI 1.02–2.98, p=<0.001 paired t-test). In five patients the operated limb overgrew the shorter limb. Conclusions. Circumferential periosteal release produces a modest decrease in both absolute and percentage limb-length discrepancy, although the outcome is variable and some patients may experience overgrowth of the operated limb