A human ribosomal protein S17 cDNA [Chen et al., Proc. Natl. Acad. Sci. USA 83 (1986) 6907-6911] was used to isolate four S17 DNA clones from human genomic libraries constructed in bacteriophage lambda and cosmid vectors. Based on its transcriptional activity in a transient expression assay and on sequence similarity with S17 cDNA, cosmid clone HGS17-6 was identified as carrying the functional RPS17 gene. RPS17 is composed of five exons and four introns that span 4 kb of DNA. Two lambda clones of human genomic DNA were recognized as containing processed S17 pseudogenes, because (i) they were transcriptionally inactive in the transient assay, and (ii) they possess multiple, perfectly spliced RPS17 exons. Their coding sequences differ slightly from the cDNA and functional genomic clone.