We have carried out cytogenetic studies on a series of ten synovial sarcomas. Five of these tumours contained the characteristic reciprocal translocation t(X;18) (p11.2;q11.2) and a further two tumours contained complex rearrangements involving chromosomes X and 18. Secondary clonal alterations were seen in four tumours. Candidate genes at Xp11.2-p11.3 have been assessed for involvement in the translocation by Northern and Southern analysis: genes encoding transcription factors (ELK1 and TFE3), a metalloproteinase inhibitor (TIMP-1), a ubiquitin-activating enzyme (UBE1), a serine-threonine kinase (ARAF1) and the neural cell phosphoprotein synapsin 1 (SYN1). We found no evidence of abnormal transcription or rearrangements of these genes in a panel of synovial sarcoma biopsies and cell lines, indicating that they are not directly involved in the t(X;18) chromosome translocation.