The processed gene L32', a member of the mouse gene family for ribosomal protein L32, could encode a 135 amino acid protein nearly identical to L32. The 5'-flanking region of the gene contains CAAT and TATA sites at positions commonly found in expressed genes. The L32' gene lies within highly methylated, DNase I-insensitive chromatin of mouse L1210 cells. Although S1 nuclease digestion studies suggested that an L32' transcript might be produced, an oligonucleotide probe specific for L32' mRNA, and RNase digestion of a cRNA probe to L32', indicated fewer than 0.1 L32' transcripts/cell. These results demonstrate that extreme caution is required when measuring transcription from related genes.