Abstract: A method of printing a receiving material wherein said receiving material is fed through a printer including a first and a second image-forming unit for substantially simultaneous printing of the front and back of said material in a transfer nip, whereby the two images are brought into register in the lateral direction with the receiving material by determining, prior to the formation of the images, a reference position at the transfer nip; forming the first image in such manner that that part of said image which corresponds to the said reference position in the transfer nip substantially coincides therewith; and also forming the second image in such a manner that part of said image which corresponds to the said reference position in the transfer nip substantially coincides therewith; and feeding the receiving material to the transfer nip in such manner that that part of said material which corresponds to the reference position coincides substantially therewith at the transfer nip.