The pollen stratigraphies of Lake Suho Breznishko (1963 m a.s.l.) and Lake Okadensko (2475 m a.s.l.) in the Northern Pirin Mountains of southwestern Bulgaria record the vegetation history since about 6000 years ago. An initial open Betula forest contained minor Pinus peuce, documented by macrofossils, as well as Abies. Conifers that had dominated at higher elevations elsewhere then expanded downslope, and after 4300 yr BP Pinus peuce was joined by Pinus diploxylon-type (including P. sylvestris, P. mugo, and P. heldreichii) and Picea. Maxima of microscopic and macroscopic charcoal, along with increases of Juniperus, Pteridium, non-arboreal pollen (including anthropogenic indicators), and algal remains, suggest significant human impact on the vegetation after about 4000 yr BP.