hv1 is a histone H2A variant found in the transcriptionally active Tetrahymena macronucleus, but not in the transcriptionally inert micronucleus. hv1 also contains antigenic determinants conserved in the histone complements of representatives of all four eukaryotic kingdoms. A cDNA clone encoding hv1 has been isolated and sequenced. Comparison of the derived protein sequence of hv1 with that of the chicken variant H2A.F and the sea urchin variant H2A.F/Z reveals remarkable homology in all but the extreme amino- and carboxy-termini and a small region in the conserved core. Putative regions of conserved antigenicity are discussed. Evidence is presented that suggests that hv1 is a single-copy, intron-containing gene that encodes a polyadenylated message. Unusual features in the 3' flanking sequence and in codon usage are also described. Evidence is also presented showing that hv1 message amounts are ten-fold greater in growing cells than in starved cells.