In order to better understand the effects of composition and properties of atmospheric residues (AR) on their reactivities for hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrodevanadium (HDV), hydrodenickel (HDNi), hydrodeasphaltene (HDAsp), and hydrodeconradson-carbon-residue (HDCCR) in the hydrotreating process, analysis and characterization of three ARs (AA-AR, AB-AR, and AM-AR) from Arabia crudes were conducted, and their hydrotreating reactivities were evaluated in a pilot unit over a catalyst system at 370 degrees C under a H-2 pressure of 13.5 MPa by comparing the conversions of the various species and their rate constants on each catalyst. The overall reactivity of various species decreases in the order of vanadium species > sulfur species approximate to asphaltenes > nickel species > Conradson carbon residue precursor > nitrogen species, regardless of the sources of the ARs. Reactivities of the three ARs in HDS, HDV, and HDAsp increase in the order of AB-AR < AA-AR < AM-AR, while reactivities of the three ARs in HDNi, HDCCR, and HDN are similar. The higher nitrogen and asphaltenes concentrations and larger density of AR have strong and negative effects on the HDS, HDV, and HDAsp reactivities but no significant effect on the HDN, HDNi, and HDCCR reactivities. The B parameter obtained from electron spin resonance analysis can be a good index to predict the HDV reactivity of A.R.