This work examines the effect of various resins and dodecyl benzene sulfonic acid (DBSA) amphiphile on asphaltene precipitation from different petroleum fluids. Various resins are added to three different petroleum fluids to measure precipitation with n-pentane. Results show that the dipole moment of resins (which is a measure of polarity) has a strong effect on precipitation. Resins with a high dipole moment are more effective than resins with a low dipole moment. The effectiveness is defined in terms of the increase in the onset point of precipitation. However, addition of resins to a petroleum fluid increases the amount of precipitated asphaltenes. This is the first report of such a behavior in the literature; the increase is less pronounced with the most polar resins. Addition of asphaltenes to a petroleum fluid results in a high amount of precipitation. As expected, the onset point of precipitation from asphaltene addition to a petroleum fluid is different from that of resins. When the DBSA amphiphile is mixed with the petroleum fluid at different concentrations, we observe a retrograde phenomenon. The amount of precipitated asphaltene increases first with increasing DBSA concentration. Beyond a certain concentration, there is a decrease in precipitation. At higher concentrations, DBSA proves to be very effective to move the onset point of precipitation. The data show the complex interactions between various species in petroleum fluids. (C) 2004 American Institute of Chemical Engineers.