The importance of early detection of lymphoedema by arm volume measurements before surgery and repeated measurements after surgery in women undergoing axillary node clearance (ANC) in order to enable early intervention is recognised. A prospective multi-centre study was performed which studied the difference between multi-frequency bioimpedance electrical analysis (BIS) and perometer arm measurement in predicting the development of lymphoedema. Women undergoing ANC underwent pre-operative and regular post-operative measurements of arm volume by both methods. The primary endpoint is the incidence of lymphoedema (≥10 % arm volume increase compared to contralateral arm by perometer) at 2 and 5 years after ANC. The threshold for intervention in lymphoedema was also assessed. Out of 964 patients recruited, 612 had minimum 6 months follow-up data. Using 1-month post-operative measurements as baseline, perometer detected 31 patients with lymphoedema by 6 months (BIS detected 53). By 6 months, 89 % of those with no lymphoedema reported at least one symptom. There was moderate correlation between perometer and BIS at 3 months (r = 0.40) and 6 months (r = 0.60), with a sensitivity of 73 % and specificity of 84 %. Univariate and multivariate analyses revealed a threshold for early intervention of ≥5 to <10 % (p = 0.03). Threshold for early intervention to prevent progression to lymphoedema is ≥5 to <10 % but symptoms alone do not predict lymphoedema. The modest correlation between methods at 6 months indicates arm volume measurements remain gold standard, although longer term follow-up is required.