High molecular weight novolak resins were prepared from phenol and paraformaldehyde in organic solvents, e.g., 2-propanol, ethyl propionate, 2-methoxyethanol, 4-methyl-2-pentanone, dioxane and acetic acid. The molecular weights were estimated by gel permeation chromatography (GPC) and solution viscosity measurement and it was confirmed that high molecular weight resins were formed in organic solvents. The structure was determined by C-13-NMR measurements, and it was found that the resin obtained in organic solvent was a random novolak with higher molecular weight than a conventional novolak.