There is considerable evidence to suggest that polypeptide growth factors from either the oviduct or the endometrium can control preimplantation development of the mammalian embryo. These act directly through receptors expressed on the embryo. In addition, embryos also produce growth factors. The reverse transcriptase-polymerase chain reaction (RT-PCR) was used to determine the pattern of expression of mRNAs encoding several growth factor ligand and receptor genes throughout preimplantation development of cryopreserved human embryos. Transcripts encoding the receptor for c-fms, the receptor for colony-stimulating factor-1 (CSF-1), and c-kit (the receptor for stem cell factor [SCF]) were expressed throughout preimplantation development. Other growth factor ligand and receptor transcripts were expressed in a stage-specific manner: these included receptors for interleukin (IL)-6 (IL-6R), leukemia inhibitory factor (LIFR), tumor necrosis factor alpha (TNF alpha) (TNFRp80 and TNFRp60), and gp130. The transcripts for gp130 and the ligand SCF showed stage-specific splice variants. Blastocysts expressed a novel cDNA encoding gp130, which predicts a truncated form lacking the intracellular signaling domain. No expression of mRNAs encoding LIF, CSF-1, or the cloned receptor for platelet-activating factor was seen in any embryonic stage studied. We have shown that RT-PCR provides a sensitive and powerful method for identifying transcripts encoding growth factors and their receptors in single human embryos. The method is economical, allowing the expression pattern of many genes to be determined from a single embryo. These data are important in defining which cytokines may be involved in regulating human preimplantation development and when they may act.