The possibility of using DNA-injected Xenopus laevis oocytes and eggs for studying the control of transcription in eukaryotes has been investigated. When purified DNA of simian virus 40 (SV40) is injected into Xenopus laevis oocytes, tritiated RNA precursors are incorporated into DNase-I-resistant, RNase-A- and alkali-sensitive material that hybridizes specifically to SV40 DNA. This viral transcription continues for at least 5 days and occurs only when the injected DNA is directed to the nucleus of the oocyte. The quantity of SV40-specific RNA produced is roughly proportional to the amount of DNA injected; above 1 ng per oocyte, most of the nonribosomal RNA made in successfully injected oocytes is virus-specific. Transcription also occurs, although at a lower efficiency, after injection of the DNA into unfertilized eggs. The DNAs of adenovirus 5, cloned Drosophila melanogaster histone genes, and even bacteriophage phiX174 replicative form, bacteriophage phi80plac, and the ColE1 plasmid are also transcribed after injection into oocytes or eggs.