The influence of different factors on the asphaltene stability in three iranian crude oils was evaluated. Compositional studies and structural characterization of resins and asphaltenes were carried out in order to study a possible relationship between these properties and asphaltene deposition behavior. Low hydrogen to carbon ratios and high aromaticities were the main characteristics of the asphaltenes from more unstable crude oils. According to these results, the stability behavior of asphaltenes was influenced strongly by their structural characteristics. Colloidal stability indexes such as the (aromatic+resins)/(asphaltene+saturates) ratio and (aromatics+resins)/ asphaltene ratio do not play a key role in the asphaltene stability for the studied crude oils.