Objective: To compare the outcome of two different culture media marketed by the MediCult AS Company (Jylinage, Denmark) Universal IVF Medium and ISM1 Medium culture which, in addition to glucose, pyruvate, and energy-providing components, also contain amino acids, nucleotides, vitamins, and cholesterol. Design: Laboratory and retrospective clinical study. Setting: University teaching hospital. Patient(s): A total of 726 patients, undergoing IVF intracytoplasmic sperm injection procedure, comparable in mean age range, oocyte retrieval, and infertility indication, were included in the study. Laboratory quality and standard procedures were maintained unaffected. Intervention(s): Oocyte retrieval, different embryo culture media. Main Outcome Measure(s): Embryo quality, ongoing pregnancy, and implantation rate. Result(s): The frequency of good-quality embryos (79% vs. 74%) and the percentages of ongoing pregnancy (27.5% vs. 18%) and implantation rate (15% vs. 10%) were significantly higher in the group treated with ISM1 Medium rather than Universal IVF Medium. Conclusion(s): ISM1 Medium culture seems to improve the performance of embryonic growth and development, as well as increasing the percentage of pregnancy. (Fertil Stetil(R) 2010;93:1859-63. (C) 2010 by American Society for Reproductive Medicine.)