The FAU gene (FBR-MuSV associated ubiquitously expressed gene) encodes the ribosomal protein S30 fused with a Ubiquitin-like molecule. The FAU gene is expressed in a wide range of tissues, is evolutionarily conserved, and has putative tumour suppressor activity in vitro. The human FAU gene maps to the long arm of chromosome 11 band q13, close to the PYGM locus. This locus is tightly linked to the Multiple Endocrine Neoplasia type 1 (MEN1) locus. The FAU gene properties, together with its chromosomal localisation on 11q13, make it a candidate gene for MEN1. To test this hypothesis we screened 33 unrelated patients with MEN1 for constitutional genetic alterations in the FAU gene by Southern blot analysis, denaturing gradient gel electrophoresis (DGGE) and in two cases complemented by DNA sequencing to confirm the DGGE data. Furthermore, 10 parathyroid and pancreatic tumours from MEN1 patients and 15 each of sporadic parathyroid and pituitary tumours were similarly examined. In addition, we studied the expression of the FAU gene at the RNA level in 9 MEN1-associated tumours by Northern blot analysis. No FAU gene anomalies could be demonstrated by any of these techniques. We conclude that FAU is not likely to be the MEN1 tumour suppressor gene.