Early mouse (n = 501) and bovine (d = 6; n = 172) embryos were obtained to evaluate the effect of a deproteinized hemodialysate (CLBl 107) on embryo development in vitro. Bovine morulae also were cultured to examine the effect of agar embedding and the environment of immature mouse uteri on embryo development. Mouse embryos were cultured for up to 96 h in M2 medium or M2 supplemented with CLBl 107. One-and two-cell embryos did not develop beyond the two-cell stage in vitro. Degeneration of one-cell embryos occurred within 36 h. Two-cell embryos degenerated sooner when cultured in M2 plus I% CLB 1107 (27.4 ± 2.5 h) than in M2 alone (41.7 ± 3.0 h). Mean final development classification of embryos cultured from the morula stage (6) in M2 supplemented with CLBI 107 was higher (9.0 ± 2) than that for morulae (8.2 ± 1) cultured in unsupplemented M2 medium. Development of embryos cultured from the blastocyst (8) or expanded blastocyst (9) stages was not affected by treatment. Agar embedded bovine embryos were cultured in Ham's F-10 and 10% steer serum either 1) immediately after collection or 2) 24 h after storage in immature mouse uteri. Non-embedded embryos were cultured in Ham's F-10 containing 3) 10% steer serum, 4) 1% CLB 1107 or 5) 1% CLB 1107 and 10% steer serum. A greater percentage of the embryos reached the hatched blastocyst stage after culture in treatments 1, 3, 4, and 5 (38.1%, 34.6%, 28.6% and 21.1%) than embryos stored in immature mouse uteri for 24 h prior to in vitro culture (9.5%). Mean final development scores for non-embedded and agar embedded embryos cultured in Ham's F-10 and 10% steer serum were not different (5.46 ± .34 and 4.89 ± .44), but were higher than embryos cultured in CLB 1107 (4.19 ± .39), CLBl 107 and steer serum (4.22 ± .44) or immature mouse uteri (3.39 ± .43). Medium supplemented with CLB 1107 did not support mouse embryo development beyond the 2-cell stage nor did it enhance bovine embryo development. However, it appeared to enhance development of mouse morulae in vitro. Additionally, bovine morulae were not affected by agar embedding in vitro and they were able to develop following short term storage in the immature mouse uterus. / M.S.