The entirety of the phosphoprotein gene of measles virus has been sequenced. The gene is composed of 1,657 nucleotides and specifies a 507-amino-acid protein (P). A second overlapping reading frame was predicted from the sequence and specifies a 186-amino-acid protein (C). Through the use of antisynthetic peptide antibodies, we show that both proteins are expressed in virally infected cells. Both proteins are expressed from a functionally bicistronic mRNA through independent initiation of ribosomes at the respective AUG codons. Using immunofluorescent microscopy, we localized the C protein in the nucleus and in cytoplasmic inclusions within the infected cells.