Overexpression of members of the myc family of oncogenes contributes to the development of many vertebrate malignancies. Although several functions for myc gene products have been proposed, the targets for Myc activity during oncogenesis or normal development remain to be identified. Oocytes of Xenopus laevis, which are non-dividing cells that accumulate abundant c-Myc protein, provide an unusual opportunity to examine c-Myc function. We have investigated whether the accumulation of massive amounts of ribosomal RNA (rRNA) by Xenopus laevis oocytes may be related to their elevated expression of myc proto-oncogenes. Our data show that anti-Myc antibodies and some (but not all) c-Myc peptides from conserved regions of the c-Myc protein enhance the turnover of rRNA synthesized in homogenates of oocyte nuclei. These results suggest that one or more members of the Myc protein family may be involved in post-transcriptional regulation of rRNA metabolism. The regulation by c-Myc of rRNA could account, in part, for the generalized stimulation of cells during tumorigenesis.