Efficient removal of deposited asphaltenes on the surface of metallic flowlines by functional molecules is investigated by nonionic and ionic surfactants at low concentrations. Deposition removal by aromatic solvent toluene is measured as a reference. Water is often coproduced with crude oil and may affect deposition of asphaltenes and removal. In this study, we investigate the effect of water in both asphaltene deposition and removal by functional molecules. Two different crudes from different fields that give rise to serious asphaltene deposition are extensively investigated. For these two crudes, we find one ionic and one nonionic surfactant to be effective in deposition removal at 1 wt% concentration in the crude. This concentration is much lower than that of the commonly studied acidic dodecylbenzene sulfonic acid (DBSA) surfactant. Toluene concentration in the crude varies from 40 to 60 wt% for asphaltene deposition removal. Water delays deposition significantly. However, water does not have an appreciable effect on performance of functional molecules on removal of deposited asphaltenes.