A gene for Saccharomyces cerevisiae tRNATrp has been sequenced which contains an intervening sequence of 34 bp (H. S. Kang and J. Abelson, unpublished results). The mutant yeast strain ts-136 accumulates a precursor to tRNATrp which contains mature ends and is colinear with the tRNATrp gene. A nuclear extract from Xenopus oocytes is capable of supporting transcription of the tRNATrp gene contained on plasmid pBR313. The products are precursor tRNAs which contain the intervening RNA sequence. The Xenopus extract accurately splices the precursor transcript to mature-sized tRNATrp.