This paper seeks a better understanding of carbonaceous mesophase through a quantitative treatment of the equilibrium phase transformations of polycyclic aromatic hydrocarbons (PAH) and pitches of known molecular weight distribution, After a brief review of the most relevant literature on discotic liquid crystals, PAH phase behavior is considered in single-component, binary and multicomponent systems. Results from recent numerical simulations of phase transitions for a generic discotic mesogen are analyzed to shed insight into the structural features favoring liquid crystal behavior. This work culminates in the formulation of a quantitative multicomponent thermodynamic model of the phase transitions in a generic carbonizing system based on virtual pure-component properties and its application to the petroleum pitch carbonization data of Greinke and Singer, (C) 1999 Elsevier Science Ltd. All rights reserved.