On behalf of the organizing committee, we cordially invite you to the XX International Roundtable of Nucleosides, Nucleotides and Nucleic Acids to be held in Montreal, Canada, August 5-9, 2012. The conference commences with an evening reception on August 5th on the McGill University Campus, and concludes with a memorable evening banquet in the heart of downtown Montreal. In between those festivities, we will have a strong and varied program of plenary sessions and contributed lectures. As in past International Roundtables (IRTs), poster presentations will form an important part of the scientific program; posters will be displayed all week and featured in two early evening sessions. We are delighted to be hosting the IRT for the first time in our beautiful city, almost 40 years after the initial IRT conference, held in Montpellier, France in 1974. Plenary lectures will be given by internationally recognized scientists, including the Montgomery and Imbach-Townsend Awardees. We will have a dynamic and engaging program with varied cutting edge research in medicinal chemistry, biochemistry, and molecular biology, as well as synthetic and therapeutic applications of nucleosides and oligonucleotides. We are confident that the IRT will be a stimulating and exciting meeting in the tradition of past IRT conferences. You will find the IRT to be conducive to scientific exchange and the city of Montreal to be an enjoyable, vibrant and stimulating location. Your participation in the conference is essential to the success of the event. The new IS3NA website will have all the information about the IRT, including registration and submission of abstracts.