A physical map of a 14.5 kb region close to the centromere on the left arm of chromosome IV of Saccharomyces cerevisiae is presented. This map has been constructed by restriction analysis of a clone from a YCp50 genomic library and by use of pre-existing and new sequence data from this region. The map reveals the following gene order (reading from the most centromere-distal to the most centromere-proximal locus): USO1/INT1-MBP1-PSA1-SLC1-YLA1 and defines the size of the open reading frames and intergenic regions.