The bryoflora of the Russian Wilderness and adjacent slopes, an area of 112.8 mi2 (292 km2), comprises only 1.8% of the land base of Siskiyou County at 6347 mi2 (16,439 km2), the fifth largest county in California. Fifty liverworts and 215 mosses (includes four undescribed taxa) are documented by voucher specimens. This represents 33% for both the liverworts and the mosses documented for California. Three species, Lophozia longidens (Lindb.) Macoun, Lophozia obtusa (Lindb.) A.Evans, and Solenostoma schusterianum (J.D.Godfrey & G.Godfrey) Váňa, Hentschel & Heinrichs are reported as new for California. Grimmia brevirostris R.S.Williams is elevated from synonomy with Grimmia hamulosa Lesq., as a species worthy of recognition and represents the first records of this California endemic for the Klamath Ranges.