Demulsification of water-in-bitumen emulsion was studied using 52 nonionic surfactants of different chemical families. Relative solubility number (RSN) and molecular weight were determined for these demulsifiers. Their dewatering performance was evaluated by determining the rate of water separation during gravitational settling and centrifugation. The results indicated that there is no overall correlation between demulsification performance and RSN value. However, within a given surfactant family, such as polymerized polyols, oxyalkylated alkylphenol formadehyde resins, and oxyalkylated alkyl resins, the degree of demulsification was found to correlate with the RSN value. A maximum of dewatering performance was observed in a specific RSN range for two surfactant families. Molecular weight also showed a significant effect on demulsification performance. Surfactants with low molecular weight (<4000) did not break the emulsion in dosages of 300-400 ppm regardless of RSN value. For the water-in-bitumen emulsion studied in this work, the most effective demulsifiers are those with RSN values between 7.5 and 12.5 and molecular weights between 7500 and 15000.