Abstract: The polypore Physisporinus rivulosus (Berk. & Curt.) Ryv. is reported as new to Finland. It is better known as Poria albipellucida Baxter and widely distributed in North America. The Finnish specimen is from Pinus sylvestris L. Though P. rivulosus is the only known species of Physisporinus Karst. with clamp connections, it otherwise fits well with that genus. The macroscopical and microscopical characteristics of P. rivulosus are described and illustrated, and the taxonomy is briefly discussed.