At present, it is possible to transfer pig embryos directly into the uterine body of sows by nonsurgical procedures. The aim of this study was to develop a procedure for nonsurgical embryo transfer (ET) into the upper part of one uterine horn in gilts and sows. In experiment 1, 29 gilts and 43 sows were used. Intrauterine insertions took place for each female at days 4-6 of the estrous cycle (D0 = onset of estrus). An artificial insemination (AI) spirette was inserted into the cervix to assist with the guidance of a modified flexible catheter originally developed for deep intrauterine insemination in pigs. The flexible catheter length inserted anterior to the inserted AI spirette was 43.0 +/- 1.7 cm. The time required to complete the procedure was affected by the type of female (P < 0.001) and by the difficulties encountered for inserting the catheter (P < 0.001). However, when no or minor difficulties were encountered during the insertion of the catheter (in approximately 70 and 80% of gilts and sows, respectively), the time required to complete the procedure did not differ between gilts (2.5 +/- 0.1 min) and sows (2.3 +/- 0.1 min). In experiment 2, 24 to 31 fresh morulae and/or blastocysts were transferred to each of 24 recipients. Seventeen animals (70.8%) farrowed an average of 6.9 +/- 0.7 piglets, of which 0.6 +/- 0.3 piglets were born dead. In conclusion, the procedure described in this study offers new possibilities to transfer embryos nonsurgically to the uterine horn of pigs.