Disclosed is the oxalic acid addition salt of 4-[(1,2,4-triazol-1-yl)methyl]benzonitrile (III). Further disclosed is a process for the preparation of 4-[(1,2,4-triazol-1-yl)methyl]benzonitrile (III), comprising the purification of the oxalic acid addition salt of 4-[(1,2,4-triazol-1-yl)methyl]benzonitrile (III), and subsequent liberation of 4-[(1,2,4-triazol-1-yl)methyl]benzonitrile (III) from the purified salt. Also disclosed is a process for the preparation of letrozole (4-[1-(4-cyanophenyl)-1-(1,2,4-triazol-1-yl)methyl]-benzonitrile), or a pharmaceutically acceptable salt thereof, wherein the process comprises the conversion of 4-[(1,2,4-triazol-1-yl)methyl)]benzonitrile (III) or the oxalic acid addition salt prepared as defined herein into Letrozole or a pharmaceutically acceptable salt thereof, wherein the 4-[(1,2,4-triazol-1-yl)methyl)]benzonitrile (III) or the salt thereof is reacted with 4-fluorobenzonitrile (IV) in the presence of a base.
