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.