100 MHz NR IX study of self-condensation of ortho- and para-methylolphenol and their co-condensation with phenol is presented Reaction rate, co-reaction with phenol, dimethylene ether and phenolic hemiformal intermediates, methylene groups distribution and reaction mechanism in different catalytic conditions are the main, topics discussed. The co-condensation rate is mainly dependent on methylolphenol reactivity and is similar with phenol and components of oil shalt alkylresorcinols.