Fourteen ribosomal protein genes from the fission yeast Schizosaccharomyces pombe contain a highly conserved sequence, CAGTCACA, in the proximal promoter. This sequence, which was also conserved in its location, was found where the TATA element usually resides. Deletion and point mutations in the CAGTCACA box reduced the expression of these genes to almost zero and caused aberrant transcriptional start sites. Insertions between this box and the original transcriptional start sites led to new start sites which were the same distance from the CAGTCACA box as the original start sites. The results presented provide evidence that this box, like a TATA sequence, is involved in basal expression and fixing the transcriptional start sites of these genes. Furthermore, the CAGTCACA sequence is the target of a binding protein which appears to be different from the TATA-binding protein.