The paper is focused on two groups of proteins inevitably important for cellulose biosynthesis in vascular plants. These are cellulose synthases and chitinase-like proteins. Cellulose synthases have been the subject of much research, and current conceptions and recent findings are reviewed in this paper. Severe effects of mutations and expression analysis have recently shown that chitinase-like proteins are crucial components of cellulose biosynthesis. However, understanding of their precise function is missed. Further research is to be prompted by an effective idea on it. I propose that chitinase-like proteins could play a role in the assembly of nascent glucan chains into microfibrills. Therefore, cellulose synthases and chitinase-like proteins are possibly sequential elements of the cellulose biosynthesis.