Objectives' To evaluate the impact of mild to moderate commissural calcification on the immediate outcomes of percutaneous balloon mitral valvuloplasty (PBMV). Methods and results' We analysed the results of 223 consecutive patients (mean age 37.6±8.7 years) who underwent PBMV for rheumatic mitral stenosis.Commissural calcification was identified with a two-dimensional echocardiography (echo) in 65 (29.1%) patients with the severity of calcification being graded from 0-3.The anatomy and function of the mitral valve were assessed by Wilkins echo score.In patients with no commissural calcification the increase in mitral valve area after PBMV was 0.90±0.42 cm2, which was greater than the increase in those with calcification grade 1 (0.83± 0.42 cm2,p<0.05), grade 2 (0.72±0.38 cm2,p<0.05) and grade 3 (0.63±0.13 cm2,p<0.05). In patients with an echo score of ?8, the presence of commissural calcification was associated with a smaller increase in mitral valve area (p<0.05) and a smaller reduction in New York Heart Association (NYHA) function class after PBMV (p<0.05). In patients with an echo score of more than 8, commissural calcification had no significant effect on the valve area increase and NYHA function class reduction (p>0.05). Conclusions' Commissural calcification has an adverse effect on the clinical results of PBMV. Detailed pre-procedural assessment of commissural calcification with echocardiography must be performed to provide background information on the immediate outcomes of PBMV.