Background and Objectives Tumor supressor gene MTS1/p16 (cyclin‐dependent kinase‐4 inhibitor) and a putative tumor metastasis supressor gene nm23 (nucleoside diphosphate A kinase) have been identified in a variety of human tumors but have not been well studied in mesenchymal neoplasms. Methods Expression of nm23 and MTS1 mRNA was determined by quantitative analysis from paraffin‐embedded tumor tissue. The series comprised 31 patients with localized primary synovial sarcoma of soft tissues who were followed for a median of 83 months. Results Neither MTS1 nor nm23 expression levels correlated with the patient's age or sex, tumor type, depth, size, mitotic rate, or extent of tumor necrosis. In addition, there was no correlation between MTS1 and nm23 levels. Patients' survival was not related to sex, age, tumor type, location, mitotic rate, or MTS1 mRNA level. The only factors that correlated with poor survival in multivariate analysis were the presence of extensive tumor necrosis (> 15%) and higher levels of nm23 mRNA. Conclusions Our results suggest that increased expression level of nm23 mRNA may be implicated in the mechanism of tumor progression and is associated with poor survival in patients with synovial sarcoma. J. Surg. Oncol. 2001;76:83–88. © 2001 Wiley‐Liss, Inc.