Sequence analysis of the L RNA genome segment and predicted encoded L polymerase protein of Crimean-Congo hemorrhagic fever (CCHF) virus (genus Nairovirus, family Bunyaviridae) demonstrates that they are approximately twice the size of those found in viruses of other bunyavirus genera. The CCHF virus L segment and encoded protein (12,164 nucleotides and 3944 amino acids, respectively) are similar in size and sequence to those of the nairovirus Dugbe virus (12,255/62% and 4036/62% nucleotide and amino acid length/identity, respectively). The identification of an ovarian tumor (OTU)-like protease motif in the L protein amino termini of the nairoviruses Dugbe, CCHF, and Nairobi sheep disease (NSD) indicates these proteins are members of the recently described OTU-like protease family and suggests that these large proteins may be polyproteins that are autoproteolytically cleaved or involved in deubiquitination.