The fouling characteristics of a desalted crude oil were investigated in a systematic investigation. There are two main parts in this study, the dry bulk tests (dehydrated crude oil) and the wet bulk tests (to which desalter brine was added). Three barrels of desalted crude oil provided by Amoco Oil Company were studied. For the dry bulk tests, no brine was added to the crude oil. The effects of fluid velocity and surface temperature on fouling were investigated. The higher the surface temperature the greater the fouling was observed. Fouling decreased with an increase of fluid velocity. Fluid velocity had a stronger effect on fouling at low surface temperatures than at high surface temperatures. It was also observed that the fouling behavior of crude oil depended on small difference in composition. The threshold surface temperatures for the initiation of fouling were 400-450 °F (3.0 ft/sec), 525-550 °F (5.5 ft/sec), 550-600 °F (8.0 ft/sec) and about 600 °F (10.0 ft/sec) for Barrel No. 2 and Barrel No. 3. For Barrel No. 1 however, the threshold surface temperatures were about 550 °F (3.0 ft/sec) and 600 °F (5.5 ft/sec). For the wet bulk tests, a certain amount desalter brine (weight percentage = 0.8%) was added to the crude oil for each run. The effects of fluid velocity, surface temperature and the presence of brine on fouling were investigated. Higher surface temperature enhanced fouling considerably. Fouling was reduced as fluid velocity was increased. It was shown that brine had a strong effect on fouling. No fouling occurred for velocities of 5.5 and 8.0 ft/sec at a surface temperature of 350 °F which was a condition for which an aqueous phase was present and the salt remained in solution. Significant fouling occurred for velocities of 5.5 and 8.0 ft/sec at a surface temperature operated at a low 400 °F (Tb = 300 °F) which was a condition for which the aqueous phase at the heat transfer surface was dissolved or boiled to extinction and the salt was deposited on the heat transfer surface.