A continuous process for the manufacture of 5-hydroxymethyl furfural (HMF), using a tube reactor and polyethyleneglycol-600 (PG-600) as the solvent was studied. The experiments were carried out at elevated temperatures and moderate acidity. Other process parameters were the residence time and the initial concentrations of D-fructose and water. The best selectivity for HMF was 65%. This selectivity can be obtained using a mixture of PG-600 and fructose with 50% by weight of fructose, for several combinations of water content, temperature, HCl-concentration and residence time. No precipitation of humin occurs. The use of PG-600 as the solvent improves the HMF formation in relation to its breakdown.