Frog virus 3 (FV3) of the Iridoviridae family has the most highly methylated DNA of any DNA virus. Its transcription presents interesting features. Although the host RNA polymerase is required for immediate early (IE) transcription, the viral DNA is not infectious and a protein component of the virion is necessary for the transcription of at least some IE genes (for review 1). The sequential expression of the FV3 genome is predominantly controlled at the level of transcription and the genes have been classified into three major groups according to their temporal expression. Regulation of this coordinate expression may partially take place via specific DNA sequences but up to now, only two immediate early genes and their promoters have been sequenced (2, 3). Having previously mapped several genes of the other classes (4), by hybrid selection of mRNAs to fragments of viral DNA and in vitro translation, we have located on fragment HindlllH a delayed early (DE) gene encoding a 3IK protein. Full expression of this gene which precedes DNA replication (5) occurs only if IE proteins are present and viral DNA replication is dependent on DE proteins. The sequence of fragment HindHIH and flanking domains has been established and is presented below. An ORF of 261 amino acids codes for a 29,525 dalton protein. The putative protein presents the particularity of having two stretches of 7 glutamic acid residues near the COOH terminus. Inverted repeat sequences, underlined, are found in the non coding regions. It is interesting to note that the 3' terminus of the 31K mRNA has been mapped by mung bean nuclease in the region comprising nucleotides 1100-1110, at the end of the inverted repeat located downstream from the ORF. This domain may function as a signal for transcription terminator or, for the mRNA, as a stabilizing hair pin (FV3 mRNAs lack poly A, 1).