Various reactions which interconvert monomers, polymers and/or macrocycles are considered and, in most cases, recent examples presented. The reactions include step-growth polymerisations, high dilution syntheses of macrocyclic oligomers, entropically-driven ring-opening polymerisations of macrocyclic oligomers, cyclo-depolymerisations to afford cyclic oligomers, and equilibrations between cyclic oligomers to give soluble combinatorial libraries of macrocycles. The latter may be screened using a soluble functionalised polymer and high resolution diffusion ordered NMR spectroscopy.