['To assess whether growth factors are produced by early human embryos in culture.', 'We studied various growth factors in the culture media of human embryos (n = 6) cultured from days 3 to 8 after fertilization.', 'Four growth factors were measured: Insulin growth factors I and II (IGF-I and IGF-II), epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) activity.', 'Nonconditioned INRA Menezo B2 (Biomerieux, S.A., Paris, France) culture medium contained significant levels of TGF alpha activity (5.2 ng/mL) and low levels of IGF-I (1.02 ng/mL) and IGF-II (2.8 ng/mL), whereas EGF was below detection of our assay. With human embryo, the culture media contained lower TGF alpha activity on days 3 and 4 after fertilization (2.5 ng/mL and 2.8 ng/mL, P less than 0.05). From days 5 to 8 after fertilization, a significant increase in TGF alpha activity and IGF-II was detected (TGF alpha activity: day 5: 3.7 ng/mL; day 6: 4.4 ng/mL; day 7: 6.4 ng/mL; day 8: 8.4 ng/mL) (IGF-II: day 5: 3.4 ng/mL; day 6: 3.1 ng/mL; day 7: 4.1 ng/mL; day 8: 4.2 ng/mL). Epidermal growth factor was undetectable, and IGF-I did not vary significantly.'] Do human embryos produce transforming growth factors alpha activity and insulin-like growth factors II?