Objective:  The hospital revenues are decreasing from the government policy in the universal coverage while increasing the hospital expenses . The cost analysis is a very important tool for the strategic plan in the hospital expenses reduction with standard quality. This study wanted  to investigate the cost of 12 orthopaedic diseases using  the clinical practice guideline (CPG) at  maximum length of stay  (LOS) and to compare the cost before  and after utilization management in cost minimization analysis in orthopaedic inpatients under the universal coverage policy.Methods:  Part 1, The CPG with maximum LOS was studied in detail and the cost analysis was performed using the formula  C = S+I+X+P+O+L+A+R  while  C = unit service cost/case, S = service cost, I = instrument cost,  X= X-ray cost,  P = prosthetic cost, O = operating cost, L = laboratory cost, A =  anesthetic cost, R = recovery room cost.  Part 2, the cost minimization analysis (CMA) before and after  utilization management was studied in 2 groups.  Group A consisted of 236 cases which were studied after utilization management from June 1, 2003 to February 24, 2005.  Group B consisted of 89 cases from June 1, 2002 to May 31, 2003  which were studied before utilization management was introduced in the department.  The cost of both groups were compared.Results:  The cost of the 12 orthopaedic diseases ranged from 13,036.10 baht/case for 3 days LOS in club foot  surgery to 99,532.73 baht/case  for 21 days LOS in total hip replacement surgery. The reduction of 1 day LOS reduces the service cost by an average 1,844.26 baht.  The  CMA  found that after utilization management in group A, the CMA in the average cost reduction was 3,274.45 baht/case  with an average 2.07 days reduction in length of stay. Both groups had the same outcomes.Conclusion:  The cost analysis was done in 12 orthopaedic diseases using CPG. The usefulness with cost reduction was found after implementation of utilization management.