The average chemical structure of asphaltenes present in a vacuum resid feed is related to the morphology of the coke that is produced in a delayed coker ( shot coke vs sponge coke). A combination of solid-state C-13 NMR, X-ray photoelectron spectroscopy ( XPS), and elemental abundance was used to characterize the average chemical structure of several n-heptane asphaltenes from shot-coke- and sponge-coke-producing vacuum resid feeds. The chemical structural properties of the asphaltenes are discussed in relation to the coke morphology produced from the parent resid. The average asphaltene aromatic carbon per cluster size is between 14 and 22 carbon atoms, which corresponds to three-to-five-ring average clusters. When the ratio of aromatic carbon to unreactive (i.e., heterocyclic aromatic) nitrogen and sulfur in asphaltenes is < 16, the feed tendency is to produce shot coke. Representative chemical structural models of asphaltenes reveal significant differences (1.5 cal/ cm(3))(1/2) in the calculated solubility parameter of the PNA core structure. Feeds with larger-solubility-parameter asphaltene PNA cores tend to produce a shot coke morphology. The differentiation appears despite much smaller differences (< 0.3 cal/cm(3))(1/2) in the solubility parameter for the full non-thermally treated asphaltene average structure. The quantity of asphaltenes and the asphaltene: concarbon ratio are not reliable predictors of coke morphology produced in delayed cokers. Microcarbon residue (MCR) tests on the vacuum resid feeds were performed, followed by cross-polarized light optical microscopy on the resultant cokes. The micrographs show a small (2- 10 mu m) domain size/anisotropy in the optically anisotropic coke produced from shot-coke-forming feeds. This is comparable to the mosaic size of commercial shot cokes. In contrast, larger flow domains of more highly anisotropic appearance are characteristic of sponge-coke-forming feeds. The approach provides a method of assessing the morphology of the coke that will be produced from a given feed.