Keeping all experimental conditions constant, feed reactivity is found to depend upon feed origin, composition, previous history, level of non-indigenous contaminants, etc. In the first part of this work, the preparative separation and characterization of the asphaltenes from seven resids of different origins and types were carried out to correlate asphaltene characteristics with feed reactivity to hydroprocessing in the presence of a Ni/Mo-dispersed catalyst (418 degrees C, 2.2 wt % molybdenum catalyst and 0.2 wt % nickel catalyst, and pressurized to 18.3 MPa of hydrogen for 2 h). Feed reactivity was measured in terms of the hydrodenitrogenation pseudo-first-order rate constant (HDN rate in h(-)1) and the percentage of reduction of microcarbon residue (% MCR). The results indicated that the hydroprocess reactivity of a given resid can be predicted reasonably well (R-2 = 0.90-0.93 range) using the concentration of asphaltenes, their aromaticity, and degree of aromatic ring condensation. In the second part, the work was focused on directly determining the asphaltene solubility characteristics of the resids and correlated them to resid reactivity to hydroprocessing. Two recently developed methods were employed: asphaltene solubility fraction and asphaltene solubility profile. The results showed that the hydroprocess reactivity can be effectively predicted with correlation factors in the 0.93-0.94 range. These results indicate that feed reactivity and asphaltene solubility are linked. Therefore, these asphaltene characterization methods can be used to estimate resid reactivity without the need of time-consuming asphaltene separation and characterization.