Embryos of Xenopus laevis (clawed frog) are an excellent model system to use in studying the effects of agents on cell division. To test the effects of conjugated linoleic acid (CLA) on cell division, X. laevis embryos were exposed to various CLA concentrations. CLA is a dienoic fatty acid found in fats developed by ruminant animals. Previous studies on rodents have shown CLA to be effective in preventing cancer, particularly breast and prostate cancer. However, the exact method by which CLA produces its chemopreventive action is unknown. A 3% water-soluble solution of CLA (from PharmaNutrients) was diluted to produce 0.1%, 0.25%, and 0.5% solutions. The embryos were incubated in these solutions and developmental rates and any abnormalities were recorded. We found that CLA slowed down the rate of cell division, produced abnormal blastomeric pigmentation and morphology, and eventually stopped development altogether. Abnormalities were not observed in the 0.1% solution until 24 hours of exposure, at which time the embryos stopped developing. The 0.25% solution slowed down cell division after 2 hours of exposure, and completely stopped development of the embryos after 3.5 hours. The highest concentration inhibited cell division and development after only 1 hour of exposure. All three solutions caused abnormal cell shape and pigmentation: individual animal blastomeres appeared to be surrounded by yolky areas, embryos seemed more easily deform-able, and animal blastomeres appeared darker than the controls.