The preparation of very narrow molecular weight distribution poly(ethylene glycol) (PEG) was investigated by fractional crystallization from solution. Fractionation experiments were conducted from the solutions of 1500, 2000, and 3000 molecular weight PEG in n-butanol/n-heptane mixtures. Size Exclusion Chromatography and Differential Scanning Calorimetric studies were performed for the characterization of fractions prepared at different crystallization temperatures and times. By suitable choice of these experimental parameters it was possible to obtain PEG fractions with M-w/M-n less than or equal to 1.05.