Several lines of evidence suggest that a number of immunoactive cytokines participate in early reproductive events such as implantation and placental development. Furthermore, cytokines may influence embryo growth and differentiation. In the present study, the production of tumour necrosis factor (TNF), interleukin-1 (IL1), interleukin-6 (IL6) and transforming growth factor-beta (TGF beta) during the first 48 h after oocyte retrieval during in-vitro fertilization was investigated. In addition, the question was raised whether soluble receptors may contribute to cytokine activity regulation in early reproduction, and concentrations of TNF and IL6 receptors in culture media were determined. Finally, an investigation of whether any association exists between cytokine concentrations and embryo morphology was performed. Media from 256 embryos were analysed. IL1, IL6 and TGF beta were produced during the 48 h culture period, whereas no TNF was detected. Levels of IL1 and IL6 were significantly higher in media from the first 24 h culture period than from the second period, whereas TGF beta concentrations in supernatants from the two observation periods did not differ. IL6 receptors were not detected, whereas TNF receptors (p75) appeared in media from the 24-48 h culture period. Granulosa, cumulus and sperm cells are potential sources of cytokine production, especially during the first 24 h period. The contribution of the embryo to cytokine/cytokine receptor production remains an open question. No significant correlation was observed between cytokine/cytokine receptor concentrations and embryo morphological score.