Background. The best way to avoid undesirable multiple pregnancies following in vitro fertilization procedure (IVF) is to perform elective single embryo transfer, but the procedure might result in a reduction of the pregnancy rates. Aim of our study was to establish whether a single blastocyst transfer using a hyaluronan rich transfer medium results in higher pregnancy rates in comparison to the transfer using a conventional transfer medium. Material and methods. Our prospective randomized study included 107 patients enrolled in the 1st, 2nd and 3rd classical IVF or intracytoplasmic sperm injection (ICSI) treatment attempt. Patients included were under 37 years of age with at least one blastocyst developed in the procedure. In the study group (47 patients) blastocyst transfers using the hyaluronan rich transfer medium were performed and in the control group (60 patients) the conventional medium was used. The pregnancy rates in the study and in the control group were compared. Results. The average pregnancy rate per single blastocyst transfer was 30 %; there were no twin pregnancies. The single blastocyst transfer using hyaluronan resulted in a non-significantly higher pregnancy rate (11 %). A significantly higher pregnancy rate with the use of hyaluronan was found in the subgroup of patients with two or more blastocysts developed in their 2nd and 3rd IVF attempt (p = 0.045). Conslusions. The single blastocyst transfer results in high implantation rates. Hyaluronan significantly contributes to higher implantation rates in a selected subgroup of patients following previous implantation failure and with multiple blastocysts developed.