Extracellular matrices and their associated growth factors can modulate the in-vitro growth of cells. In this study, the effects of culture substrata and the cytokine interleukin-6 (IL-6) on embryonic development were investigated. In-vitro fertilized mouse oocytes were pooled and randomly distributed amongst treatment groups. The test treatments were: (i) IL-6, at either 500 or 1000 pg/ml; (ii) human extracellular matrix (HECM) applied to organ culture dishes at either 5.0 or 10.0 microg/ml; and (iii) HECM and IL-6 combined. A total of 1285 embryos was evaluated. The effect of IL-6 on embryos was dose dependent. Treated embryos exhibited higher blastulation and hatching rates than untreated control embryos. Culture of embryos on human matrix proteins versus standard culture surfaces significantly improved in-vitro hatching. The combination of both of these treatments was superior to the medium alone control, and the mean cell count per blastocyst was higher (131.7 +/- 29.7 versus 82. 5 +/- 14.3 in control embryos; P < 0.0001). In a pilot study with human triploid embryos, the HECM/IL-6 culture system appeared to support embryonic compaction, blastulation and hatching. This work suggests that extracellular matrix components in combination with growth factors/cytokines may be another avenue for formulating more physiological culture systems.