The effect of passage through the digestive tract of Bison bison on the recovery and germinability of undamaged passed seeds of Pseudoroegneria spicata, Elymus cinereus, Oryzopsis hymenoides, Stipa comata, Balsamorhiza sagittata and Sphaeralcea coccinea was tested. Recovery of undamaged passed seeds peaked 2 days after ingestion and then decreased to the lowest level on day 5 of sample collection for all species used, but the pattern of seed passage through time significantly differed among species. Recovery of passed seeds was greatest for round-shaped, hard seed-coated O. hymenoides and lowest for largest seed-sized B. sagittata. The digestive tract of B. bison did not break seed dormancy of O. hymenoides, S. comata, S. coccinea or B. sagittata. Germination percentage of P. spicata and E. cinereus seeds decreased compared with unpassed seeds of the same species.