The complete nucleotide sequence of RNA segment 7 of influenza C/California/78 virus was determined by using cloned cDNA derived from viral RNA. The gene is 934 nucleotides long and possesses a long open reading frame which can code for a protein of 286 amino acids. Hybrid arrest translation experiments with the cloned cDNA fragment and poly(A)-containing RNA isolated from virus-infected cells showed that a 28,500-molecular-weight protein is coded for by RNA 7. Comparison of the proteins induced in the cell-free system and in virus-infected cells with those found in purified virus suggests that the 28,500-molecular-weight protein is a nonstructural protein.