The cryptopleurine resistance gene, cry1, of Saccharomyces cerevisiae has been molecularly cloned using genetic complementation of cryptopleurine sensitivity by the cryptopleurine resistance gene contained in a clone library prepared from DNA of a cryptopleurine resistant strain. Analysis of RNA transcripts indicated that the cry1 gene is the template for a transcript of approximately 900 bases and that the primary transcript contains an intron of approximately 300 bases. In vitro hybrid selection translation experiments indicated that this transcript encodes a protein of molecular weight 17 kilodaltons which on two-dimensional SDS polyacrylamide gels exactly coincides with ribosomal protein rp59. Further analysis showed that when the gene was present on a plasmid of about five copies per cell the amount of messenger RNA was elevated approximately five-fold compared to a cell that had only a single chromosomal copy. The rate of synthesis of ribosomal protein rp59 was not detectably elevated. These data suggest that the cry1 gene is regulated, at least in part, post-transcriptionally.