The variability of sperm histones in frogs has been studied by cytochemical and amino acid analyses. Cytochemically, Rana sperm proteins fall into Bloch's ('69, '76) type 4 somatic-like histone category, while Xenopus and Bufo have type 3 intermediate sperm histones. Extractability in 5% trichloroacetic acid (TCA) at different temperatures splits this type 3 category into two groups: type 3B intermediate sperm histones of Bufo are extractable at 85-90 degrees C, while Xenopus intermediate type 3A sperm histones require temperatures of 95-100 degrees C for extraction. Amino acid analysis confirms that Rana sperm histones are of the nucleosomal type, with a testis-specific, very lysine-rich H1 histone. The sperm protein in Bufo is richer in arginine than the proteins in Xenopus. Both of these genera contain lysine and histidine as well as arginine in their sperm proteins. These results confirm earlier electrophoretic data (Kasinsky et al., '78) and indicate that sperm histones in the order Anura can vary markedly between different genera.