Infertility is a widespread problem around the world, although the available treatment options constantly improve through research and methodological development. A common treatment option mainly for biologically caused infertility is in-vitro fertilization, where in a menstrual cycle multiple oocytes are stimulated to mature and are then fertilized in a laboratory. This often results in multiple good quality embryos which can be cryopreserved through vitrification and used in a later cycle to increase the success chance of the treatment. The purpose of this pilot study was to evaluate vitrification and warming kits from Kitazato and Irvine Scientific regarding results and procedures. Human cleavage stage embryos (n=76) were thawed and cultured to the blastocyst stage. The blastocysts were scored according to Gardner and cryopreserved with vitrification and warming kits from either Kitazato (n=20) or Irvine Scientific (n=20). The warmed blastocysts were controlled after 2 and 4 hours for re-expansion and freeze injuries. The data was analysed with Fisher’s exact test and considered statistically significant if two-tailed p-value <0.05. The results showed no significant difference between the kits after 2 respectively 4 hours regarding re-expansion (p=0.432; p=0.492) or freeze injury (p=1.000; p=0.476). A significant difference was observed between group AB (with higher Gardner-score) and group C (with lower Gardner-score) in the degree of freeze injury (p=0.048; p=0.034), regardless of vitrification kit used. The details of the procedures differed somewhat between the kits, both having pros and cons, although overall procedures were equivalent. Further evaluation is needed before a change in method can be conducted.