This study investigated the synthesis of Xenopus histones during erythropoiesis. Although cessation of DNA replication in the mid‐stages of erythroid maturation is accompanied by arrested synthesis of histone H1 and core histones, synthesis of H1 s (an H1°‐like histone) was found to continue into late stages of erythropoiesis, as has been reported for avian erythrocyte histone H5. This was accompanied by a threefold increase in the relative amount of Xenopus H1 s , similar to the accumulation reported for H5 during avian erythropoiesis and for H1° in some differentiated mammalian cells. The structural and metabolic homologies of avian H5, mammalian H1°, and Xenopus H1 s imply that these lysine‐rich histones have closely related functions distinct from those of H1, and thus represent a subclass of lysine‐rich histones.