The present invention relates to a process for the production of paper which comprises: (a) providing an aqueous cellulosic suspension; (b) separately adding to the suspension: (i) a nitrogen-containing organic compound having a molecular weight less than 1,000; and (ii) a cellulose-reactive sizing agent; and (c) dewatering the obtained suspension to form paper. The invention further relates to a process in which a nitrogen-containing organic compound having a molecular weight less than 1,000 is mixed with an aqueous dispersion of a cellulose-reactive sizing agent to form a pre-mix and which premix is added to the suspension.