INTRODUCTION *Work attributed to Department of Pediatric Orthopaedics, Chacha Nehru Bal Chikitsalaya, Geeta Colony, Delhi-110031(India)This study tested the hypothesis whether the lymphocyte/monocyte ratio (L/M ratio) altered significantly during treatment of paediatric osteoarticular tuberculosis (OATB) for it to be a useful monitor of the response to therapy. MATERIAL AND METHODS Thirty immunocompetent paediatric patients with OATB treated with 6 months of uninterrupted multidrug anti-tubercular treatment with resultant clinical and radiological healing of the lesion were included. Haemoglobin, total leucocyte, monocyte and lymphocyte count, and erythrocyte sedimentation rate (ESR) were collected at 0, 2 and 6 months, and were analysed. RESULTS The L/M ratio altered from high (11) at the start of treatment towards normalisation (9) at 2 months and (7.7) at 6 months. There was no correlation with declining ESR levels. CONCLUSIONS The L/M ratio may have potential as an effective biomarker response.